In this document we refer to terms like 'L2 device', 'L2/L3 hybrid', etc. Here are our definitions:

L2 Device
A device that functions as a Layer 2 (Ethernet) Bridge (a.k.a. 'switch', 'bridge', 'hub', etc).

L3 Device
A device that functions as a L3 (IP) router only. This means it does not bridge any Ethernet frames between its interfaces. Such a device is typically called a 'router'.

L2/L3 Hybrid
A device that functions both as a L2 bridge and a L3 router. This means it can both bridge Ethernet frames between its interfaces as well as route IP traffic and participate in IP routing protocols. Foundry/Brocade, Force10 and Extreme are common examples of this type of device.

In this document we refer to terms like 'L2 device', 'L2/L3 hybrid', etc. Here are our definitions:

L2 Device
A device that functions as a Layer 2 (Ethernet) Bridge (a.k.a. 'switch', 'bridge', 'hub', etc).

L3 Device
A device that functions as a L3 (IP) router only. This means it does not bridge any Ethernet frames between its interfaces. Such a device is typically called a 'router'.

L2/L3 Hybrid
A device that functions both as a L2 bridge and a L3 router. This means it can both bridge Ethernet frames between its interfaces as well as route IP traffic and participate in IP routing protocols. Foundry/Brocade, Force10 and Extreme are common examples of this type of device.

A photonic switch introduces less than 3 dB of attenuation between the AMS-IX patch panel and the Ethernet access switch. A switchover between the two topologies introduces a very short link flap (typically < 20 ms). In order to avoid BGP instability, you should configure your router to ignore such events.

Most vendors implement specific commands to ensure BGP ignores such events (see '10GE specifics' in the respective vendor sections for Cisco, Force10. Foundry/Brocade and Juniper configurations). If your router platform does not support such a feature, we advise you to configure the equivalent of:

A photonic switch introduces less than 3 dB of attenuation between the AMS-IX patch panel and the Ethernet access switch. A switchover between the two topologies introduces a very short link flap (typically < 20 ms). In order to avoid BGP instability, you should configure your router to ignore such events.

Most vendors implement specific commands to ensure BGP ignores such events (see '10GE specifics' in the respective vendor sections for Cisco, Force10. Foundry/Brocade and Juniper configurations). If your router platform does not support such a feature, we advise you to configure the equivalent of:

To ignore link flaps and wait for the BGP hold timers to expire before resetting sessions.

To ignore link flaps and wait for the BGP hold timers to expire before resetting sessions.

Each equipment vendor implements its own maximum ages for the IPv4 ARP and IPv6 neighbor caches. The values vary widely and in at least one case (Linux) it is not a constant.Low ARP timeouts can lead to excessive ARP traffic, especially if the values are lower than the BGP KEEPALIVE interval timers. On the other hand, long timeouts can theoretically lead to longer downtime if you change equipment (since your peers still have the old MAC address in their ARP cache). With BGP this is unlikely to happen because your router will start re-establishing BGP sessions as soon as it is back up, causing its peers to update their ARP cache as well.

We recommend setting the ARP cache timeout to at least two hours, preferably four (240 minutes). See the sections on specific equipment vendors for examples.

Each equipment vendor implements its own maximum ages for the IPv4 ARP and IPv6 neighbor caches. The values vary widely and in at least one case (Linux) it is not a constant.Low ARP timeouts can lead to excessive ARP traffic, especially if the values are lower than the BGP KEEPALIVE interval timers. On the other hand, long timeouts can theoretically lead to longer downtime if you change equipment (since your peers still have the old MAC address in their ARP cache). With BGP this is unlikely to happen because your router will start re-establishing BGP sessions as soon as it is back up, causing its peers to update their ARP cache as well.

We recommend setting the ARP cache timeout to at least two hours, preferably four (240 minutes). See the sections on specific equipment vendors for examples.

The IPv4 prefix for the AMS-IX peering LAN (1.7.246.0/24) is part of AS 141809, and is not supposed to be globally routable. This means the following:

• Do not configure 'network 1.7.246.0/24' in your router's BGP configuration (seriously, we have seen this happen!).
• Do not redistribute the route, a supernet, or a more specific outside of your AS. We (AS141809) announce it with a no-export attribute, please honour it.

In short, you can take the view that the Peering LAN is a link-local address range and you may decide to not even redistribute it internally (but in that case you may want to set a static route for management access so you can troubleshoot peering, etc.).

The IPv4 prefix for the AMS-IX peering LAN (1.7.246.251.0/24) is part of AS141809, and is not supposed to be globally routable. This means the following:

• Do not configure 'network 1.7.246.251.0/24' in your router's BGP configuration (seriously, we have seen this happen!).
• Do not redistribute the route, a supernet, or a more specific outside of your AS. We (AS141809) announce it with a no-export attribute, please honour it.

In short, you can take the view that the Peering LAN is a link-local address range and you may decide to not even redistribute it internally (but in that case you may want to set a static route for management access so you can troubleshoot peering, etc.).

Please exchange only unicast routes over your BGP sessions in the ISP peering LAN. Exchanging multicast routes is useless since multicast traffic is not allowed on the (unicast) ISP peering LAN.

Please exchange only unicast routes over your BGP sessions in the ISP peering LAN. Exchanging multicast routes is useless since multicast traffic is not allowed on the (unicast) ISP peering LAN.

The AMS-IX rules dictate that only one MAC address is allowed behind a port. This means that you have to be extremely careful when connecting a device that can act as a L2 device.

We allow only one MAC address because we allow no additional devices behind the AMS-IX ports. Extended L2 networks are not under the control of AMS-IX, but instabilities in a L2 network behind the AMS-IX switches can and typically do have a negative impact on the whole exchange. Forwarding loops and spanning tree topology changes are good examples of this. By enforcing the one-MAC-address-per-port rule, we effectively prevent forwarding loops and STP traffic from intermediate L2 devices.

In short, an intermediate L2 device may only bridge frames from the member's router to the AMS-IX port (so we see only one MAC address) and should otherwise be completely invisible. No connected device should bridge frames from other devices onto AMS-IX, or talk STP on its AMS-IX interface.

4.1.1 Connecting a L3 Device

The most preferred way of connecting to AMS-IX is directly through a L3 device (router), see the diagram below. This is your best chance of not leaking MAC addresses or STP traffic and it greatly increases the stability of the network.

The AMS-IX rules dictate that only one MAC address is allowed behind a port. This means that you have to be extremely careful when connecting a device that can act as a L2 device.

We allow only one MAC address because we allow no additional devices behind the AMS-IX ports. Extended L2 networks are not under the control of AMS-IX, but instabilities in a L2 network behind the AMS-IX switches can and typically do have a negative impact on the whole exchange. Forwarding loops and spanning tree topology changes are good examples of this. By enforcing the one-MAC-address-per-port rule, we effectively prevent forwarding loops and STP traffic from intermediate L2 devices.

In short, an intermediate L2 device may only bridge frames from the member's router to the AMS-IX port (so we see only one MAC address) and should otherwise be completely invisible. No connected device should bridge frames from other devices onto AMS-IX, or talk STP on its AMS-IX interface.

4.1.1 Connecting a L3 Device

The most preferred way of connecting to AMS-IX is directly through a L3 device (router), see the diagram below. This is your best chance of not leaking MAC addresses or STP traffic and it greatly increases the stability of the network.

4.1.2 Connecting Through a L2 Device

We neither recommend nor encourage connecting your router through a L2 device, but if you do so, keep the following in mind:

• You must make absolutely sure that only traffic to/from your L3 router's interface goes to/from the AMS-IX port.
• You must make absolutely sure that all legitimate traffic to/from your L3 router's interface goes to/from the AMS-IX port.
  • MLD snooping may block legitimate ICMPv6 neighbour solicitations.
• You must disable spanning tree on your link to AMS-IX.

4.1.2 Connecting Through a L2 Device

We neither recommend nor encourage connecting your router through a L2 device, but if you do so, keep the following in mind:

• You must make absolutely sure that only traffic to/from your L3 router's interface goes to/from the AMS-IX port.
• You must make absolutely sure that all legitimate traffic to/from your L3 router's interface goes to/from the AMS-IX port.
  • MLD snooping may block legitimate ICMPv6 neighbour solicitations.
• You must disable spanning tree on your link to AMS-IX.

On all intermediate L2 devices, consider using explicitly defined port-based VLANs for production ports. It forces you to understand your topology and reduces the chances of a nasty surprise further down the road. In particular, we strongly recommend using a dedicated VLAN for the path from your router to AMS-IX.

4.1.3 Connecting a L2/L3 Hybrid

The L2/L3 hybrid switch/router requires careful configuration in order to prevent unwanted traffic from leaking onto the exchange. As with intermediate L2 devices, you need to keep the following in mind:

• You must make absolutely sure that your AMS-IX port is configured as a 'router only' port.
• You must disable Spanning Tree on your link to AMS-IX.

On all intermediate L2 devices, consider using explicitly defined port-based VLANs for production ports. It forces you to understand your topology and reduces the chances of a nasty surprise further down the road. In particular, we strongly recommend using a dedicated VLAN for the path from your router to AMS-IX.

4.1.3 Connecting a L2/L3 Hybrid

The L2/L3 hybrid switch/router requires careful configuration in order to prevent unwanted traffic from leaking onto the exchange. As with intermediate L2 devices, you need to keep the following in mind:

• You must make absolutely sure that your AMS-IX port is configured as a 'router only' port.
• You must disable Spanning Tree on your link to AMS-IX.

On a L2/L3 hybrid device, it is a good idea to put the AMS-IX connected interface (untagged) in a separate (non-default) port-based VLAN without spanning tree and with no other ports in it. This is the best way to ensure that no traffic from other ports will be bridged onto the AMS-IX port.

On a L2/L3 hybrid device, it is a good idea to put the AMS-IX connected interface (untagged) in a separate (non-default) port-based VLAN without spanning tree and with no other ports in it. This is the best way to ensure that no traffic from other ports will be bridged onto the AMS-IX port.

Any traffic other than the types mentioned in the previous section is deemed to be illegal traffic. In this section we will list some of the more common types of violations we see at AMS-IX and give some arguments as to why it is considered unwanted.

4.2.1 Multiple MAC addresses

Since AMS-IX operates on the principle of one router per port, there should be one MAC address visible behind each port. Some members connect through intermediate switches, or use a L2/L3 hybrid device. If these devices are not configured properly, they can cause forwarding loops, STP instabilites, and lots of unwanted traffic on the exchange. There is no excuse for these devices to leak traffic, and there is no necessity to talk STP on the link to AMS-IX. Hence, by enforcing the one-MAC-address rule, we also enforce these issues. Beware that this rule is enforced automatically, so if you leak traffic from another MAC address, your legitimate traffic may be blocked (depending on which MAC address the switch sees first)!

4.2.2 Spanning Tree (STP)

This point is closely related to the previous point. The device(s) connected to the AMS-IX port are not allowed to be visible as L2 bridges. This means that they should not speak STP (spanning tree) or any other (proprietary) L2 specific protocol.

4.2.3 Routing protocols: EIGRP, OSPF, RIP, IS-IS

The only routing protocol allowed on AMS-IX is BGP. There is no valid reason for interior routing protocols to appear on the shared medium. These protocols only cause unnecessary multicast and broadcast traffic.

4.2.4 (Cisco) Keepalive

By default Cisco routers and switches periodically test their (Fast) Ethernet links by sending out Loopback frames (ethertype 0x9000) addressed to themselves. Call it a 'L2 self-ping' if you will. In a switched environment it can be used to test the functionality of the switch and/or keep the router's MAC address in the switch's address table.

In the AMS-IX environment, this is not useful since we use MAC timeouts that are larger than the typical BGP and/or ARP timeouts. In fact, the keepalives a may actually cause port security violations if they are being sent by an intermediate switch.

4.2.5 Discovery protocols: CDP, EDP, LLDP

Various vendors (e.g. Extreme, Cisco) tend to ship their boxes as gregarious devices: by default they announce their existence out of all their interfaces and try to find family members. CDP (Cisco) and EDP (Extreme) are examples of this, but there are others.

The only reason for running discovery protocols is to support certain types of autoconfiguration. Autoconfiguration on an Internet Exchange is a very bad idea. Hence, there is absolutely no reason to run discovery protocols on your AMS-IX interface. Discovery protocols typically cause unwanted broadcast or multicast traffic.

4.2.6 Non-unicast IPv4: IGMP, DHCP, TFTP

On the ISP peering LAN, the only non-unicast traffic that is allowed is the ARP query.Sometimes we see equipment trying to get a configuration through broadcast TFTP, or configure themselves through DHCP. These options are unsafe and we strongly advise against them.Other equipment has IGMP turned on by default (or by accident). The Peering LAN is for unicast IP traffic only, so there is no point in configuring multicast on the AMS-IX interface.

4.2.7 Proxy ARP

Since traffic over AMS-IX is exchanged based on BGP routes, there is no reason to answer ARP queries for any other IP address(es) than those that are configured on your AMS-IX interface.Unfortunately, some vendors (e.g. Cisco) ship their products with proxy ARP enabled by default.Proxy ARP is not only sloppy, it can lead to unwanted traffic on your network. Consider that if you have it enabled at AMS-IX, it's likely to be enabled at other peering points, allowing parties on both sides to use you as a transit.Proxy ARP is not allowed.

4.2.8 Non-unicast IPv6: IPv6 ND-RA

IPv6 router advertisements are not allowed: they generate a lot of unnecessary traffic, since IPv6 hosts on AMS-IX are not autoconfigured and besides, you don't want to be the default router for AMS-IX as a whole.

4.2.9 Miscellaneous non-IP: DEC MOP, etc.

Some vendors enable protocols other than IP by default. Cisco, for example ships certain versions of IOS with DEC MOP enabled by default. This is non-IP traffic and has no place on AMS-IX.

Any traffic other than the types mentioned in the previous section is deemed to be illegal traffic. In this section we will list some of the more common types of violations we see at AMS-IX and give some arguments as to why it is considered unwanted.

4.2.1 Multiple MAC addresses

Since AMS-IX operates on the principle of one router per port, there should be one MAC address visible behind each port. Some members connect through intermediate switches, or use a L2/L3 hybrid device. If these devices are not configured properly, they can cause forwarding loops, STP instabilites, and lots of unwanted traffic on the exchange. There is no excuse for these devices to leak traffic, and there is no necessity to talk STP on the link to AMS-IX. Hence, by enforcing the one-MAC-address rule, we also enforce these issues. Beware that this rule is enforced automatically, so if you leak traffic from another MAC address, your legitimate traffic may be blocked (depending on which MAC address the switch sees first)!

4.2.2 Spanning Tree (STP)

This point is closely related to the previous point. The device(s) connected to the AMS-IX port are not allowed to be visible as L2 bridges. This means that they should not speak STP (spanning tree) or any other (proprietary) L2 specific protocol.

4.2.3 Routing protocols: EIGRP, OSPF, RIP, IS-IS

The only routing protocol allowed on AMS-IX is BGP. There is no valid reason for interior routing protocols to appear on the shared medium. These protocols only cause unnecessary multicast and broadcast traffic.

4.2.4 (Cisco) Keepalive

By default Cisco routers and switches periodically test their (Fast) Ethernet links by sending out Loopback frames (ethertype 0x9000) addressed to themselves. Call it a 'L2 self-ping' if you will. In a switched environment it can be used to test the functionality of the switch and/or keep the router's MAC address in the switch's address table.

In the AMS-IX environment, this is not useful since we use MAC timeouts that are larger than the typical BGP and/or ARP timeouts. In fact, the keepalives a may actually cause port security violations if they are being sent by an intermediate switch.

4.2.5 Discovery protocols: CDP, EDP, LLDP

Various vendors (e.g. Extreme, Cisco) tend to ship their boxes as gregarious devices: by default they announce their existence out of all their interfaces and try to find family members. CDP (Cisco) and EDP (Extreme) are examples of this, but there are others.

The only reason for running discovery protocols is to support certain types of autoconfiguration. Autoconfiguration on an Internet Exchange is a very bad idea. Hence, there is absolutely no reason to run discovery protocols on your AMS-IX interface. Discovery protocols typically cause unwanted broadcast or multicast traffic.

4.2.6 Non-unicast IPv4: IGMP, DHCP, TFTP

On the ISP peering LAN, the only non-unicast traffic that is allowed is the ARP query.Sometimes we see equipment trying to get a configuration through broadcast TFTP, or configure themselves through DHCP. These options are unsafe and we strongly advise against them.Other equipment has IGMP turned on by default (or by accident). The Peering LAN is for unicast IP traffic only, so there is no point in configuring multicast on the AMS-IX interface.

4.2.7 Proxy ARP

Since traffic over AMS-IX is exchanged based on BGP routes, there is no reason to answer ARP queries for any other IP address(es) than those that are configured on your AMS-IX interface.Unfortunately, some vendors (e.g. Cisco) ship their products with proxy ARP enabled by default.Proxy ARP is not only sloppy, it can lead to unwanted traffic on your network. Consider that if you have it enabled at AMS-IX, it's likely to be enabled at other peering points, allowing parties on both sides to use you as a transit.Proxy ARP is not allowed.

4.2.8 Non-unicast IPv6: IPv6 ND-RA

IPv6 router advertisements are not allowed: they generate a lot of unnecessary traffic, since IPv6 hosts on AMS-IX are not autoconfigured and besides, you don't want to be the default router for AMS-IX as a whole.

4.2.9 Miscellaneous non-IP: DEC MOP, etc.

Some vendors enable protocols other than IP by default. Cisco, for example ships certain versions of IOS with DEC MOP enabled by default. This is non-IP traffic and has no place on AMS-IX.

Global configuration

Global configuration

Interface configuration

Interface configuration

It is difficult to give a complete guide for Cisco products, because of the many different types of devices and (IOS) software versions. When in doubt, consult your documentation.

5.3.1 29xx and 35xx Series

If you use a Cisco Layer 2 device (such as the 2900 and 3500 series), you have to turn off VTP (VLAN Trunking Protocol), DTP (Dynamic Trunking Protocol), LLDP, and UDLD.

In global config mode:

It is difficult to give a complete guide for Cisco products, because of the many different types of devices and (IOS) software versions. When in doubt, consult your documentation.

5.3.1 29xx and 35xx Series

If you use a Cisco Layer 2 device (such as the 2900 and 3500 series), you have to turn off VTP (VLAN Trunking Protocol), DTP (Dynamic Trunking Protocol), LLDP, and UDLD.

In global config mode:

5.3.2 7600 Series

Members are advised not to run 12.2(33)SRC on their Cisco 7600's with a sup720. This software release does not always send or forward replies to solicit requests, even if it's acting as a pure Layer 2 switch between a member router and the AMS-IX fabric.

To make a Cisco 7600 switch 'silent' the following configuration seems to work:

5.3.2 7600 Series

Members are advised not to run 12.2(33)SRC on their Cisco 7600's with a sup720. This software release does not always send or forward replies to solicit requests, even if it's acting as a pure Layer 2 switch between a member router and the AMS-IX fabric.

To make a Cisco 7600 switch 'silent' the following configuration seems to work:

Vlan XX was also removed from the 'allow list' on all dot1q trunk ports not related to the setup, in this case every dot1q trunk port in the chassis.

5.3.3 Catalyst 6500 Series

CatOS and IOS are different beasts, so for Catalyst switches, the following applies:

Vlan XX was also removed from the 'allow list' on all dot1q trunk ports not related to the setup, in this case every dot1q trunk port in the chassis.

5.3.3 Catalyst 6500 Series

CatOS and IOS are different beasts, so for Catalyst switches, the following applies:

If, for some reason, you cannot afford to turn off VTP globally, the only way to turn it off on individual ports seems to be by using l2pt:

If, for some reason, you cannot afford to turn off VTP globally, the only way to turn it off on individual ports seems to be by using l2pt:

Depending on your CatOS platform, you may or may not be able to do this.

5.3.4 CRS (IOS-XR)

CDP, Proxy ARP, Directed Broadcast, Link Auto Negotiation, and ICMP redirects* are disabled by default in IOS-XR. ICMP redirect messages are disabled by default on the interface unless the Hot Standby Router Protocol (HSRP) is configured.

5.3.5 Other Devices

For other devices, some or all of the above may apply. Check your documentation for details.

Depending on your CatOS platform, you may or may not be able to do this.

5.3.4 CRS (IOS-XR)

CDP, Proxy ARP, Directed Broadcast, Link Auto Negotiation, and ICMP redirects* are disabled by default in IOS-XR. ICMP redirect messages are disabled by default on the interface unless the Hot Standby Router Protocol (HSRP) is configured.

5.3.5 Other Devices

For other devices, some or all of the above may apply. Check your documentation for details.

5.4.1 Catalyst 6500 Series

Configure the port-channel as on, or should you want LACP, as active. Please do not not configure any forms of negotiate or desirable as the AMS-IX switches do not speak PAgP.

Load-balancing over four ports may result in an unequal distribution due to bug CSCsg80948.

5.4.1 Catalyst 6500 Series

Configure the port-channel as on, or should you want LACP, as active. Please do not not configure any forms of negotiate or desirable as the AMS-IX switches do not speak PAgP.

Load-balancing over four ports may result in an unequal distribution due to bug CSCsg80948.

Here are examples of LACP configurations:

Here are examples of LACP configurations:

5.4.2 GSR Series

Do not set a static MAC address on the Port-channel interface. This causes CEF inconsistencies and other assorted failures.Link aggregation and IPv6 do not seem to play well together. Cisco advises against trying this.

Some changes will result in a different MAC address getting chosen for the aggregated link (likely such as reloading a linecard, if it contains the first port in the bundle). This will keep your ports dysfunctional due to port security on the AMS-IX switches and you will have to contact the AMS-IX NOC in such cases to fix this.

Some restrictions apply to what features are supported on link bundles (e.g. sampled NetFlow only on ISE/Engine4+; no uRPF). Also not all line cards support link bundling, and if traffic towards AMS-IX comes in on such an interface you will experience suboptimal load-balancing. Please see the Cisco documentation for more details.

Support for link bundling on Engine 5 linecards will come in 12.0(33)S.Cisco Engineering have a special train called 'Phase 3' (lb-eft-ph3) that is purported to also provide functionality such as MAC address accounting for Port-Channel interfaces. This seems to have been integrated into 12.0(32)S, but IPv6 does not seem to be supported yet.

Below follows a list of Cisco Bug IDs (ddts) related to link aggregation that you need to consider when choosing an appropriate IOS image

CSCee27396
present in 12.0(26)S1; fixed in 12.0(26)S3, 12.0(27)S2, 12.0(28)S1, 12.0(30)SSymptoms: Over 90% CPU usage by CEF Scanner on all linecards and %TFIB-7-SCANSABORTED errors occur when configuring a link bundle. Also, the router sends traffic to MAC addresses taken from its ARP table seemingly at random, instead of to the appropriate next-hop's MAC address.

CSCef12828
present in post-CSCee27396; fixed in 12.0(26)S4, 12.0(27)S3, 12.0(28)S1, 12.0(30)SSymptoms: When traffic passes through a router, the router blocks traffic for certain prefixes behind a port-channel link.

CSCdz33664
present in 12.0(25)S3, 12.0(26)S1, 12.0(27)S2, 12.0(28)S; fixed in 12.0(25)S4Symptoms: An HSRP state change on any Engine2 interface causes a microcode bundle flap on all other Engine2 linecards, preventing load balancing to work due to vanilla microcode getting loaded.

CSCee81071
present in 12.0(26)S3, 12.0(27)S2, 12.0(29)SSymptoms: Router sends Ethernet frames with a source MAC address of beef.f00d.beef and destination MAC address f00d.beef.f00d (which is the pattern scribbled in unallocated memory in linecards), with what looks to be a legitimate payload of transit traffic. This is one of the symptoms of CSCee27396

CSCeb38014
present in 12.0(26)S5; fixed in 12.0(26)S5, 12.0(27)SSymptoms: The BGP Router process flushes the BGP tables for each peer when you change one neighbor's description. This pegs the GRP CPU at 99% for quite a while.

CSCeg31951
present in 12.0(31)S; fixed in 12.0(31)S2 (CSCei53226)
Symptoms: IOS (at least in the PRP code) places each individual public peer in its own update-group if remove-private-as is configured on a peer. Needless to say, this scales badly for a router connected to an Internet exchange. (Try 'show ip bgp replication'.) A collection of hearsay follows for recent IOS images for the GSR PRP regarding link aggregation. AMS-IX does not run any GSRs. Please take this information with appropriately-sized grains of salt.

• 12.0(24)S2 is not advisable (not many specifics known but they include CSCef89562 and CSCee33045)
• 12.0(24)S6 boots but load-balancing is completely off 12.0(25)S until S3 have CSCdz33664
• 12.0(26)S until S4 have CSCef89562, where Engine4+ linecards can have continuously flapping interfaces, but is also somewhat required for Quadra linecards
• 12.0(26)S3 has CSCee27396 integrated but not CSCef12828, which leads to traffic blackholing 12.0(27)S until S3 have CSCef89562 as well
• 12.0.(27)S1 has a problem where it sends traffic to random destinations 12.0(27)S2 has CSCee27396 integrated but not CSCef12828
• 12.0(27)S4 reportedly works reasonably well on PRP2s
• 12.0(28)S1 has problems with Engine2 linecards (CSCef78098) and Engine4+ (CSCef89562)
• 12.0(28)S2 reportedly works better but still sometimes emits beef.f00d.beef frames on normal ports with only an IPv6 address configured
• 12.0(30)S has only been observed to exhibit CSCef12828-like symptoms in conjunction with broken hardware, and also (sometimes) to still emit frames from MAC beef.f00d.beef.
• Routers occasionally still send out frames with beef.f00d.beef as MAC source address on interfaces with an IPv6 but no IPv4 address configured, even on regular links.
• Due to the massive amount of feature requests there will be both a 12.0(32)S and a new 12.0(32)SY train.

You can check for incorrect next-hops by attaching to the linecard and executing show controllers rewrite and show adjacency internal and comparing the two rewrite strings for a certain peer's IPv4 address (suffix the commands with | begin 80.249.20a.b). The first six bytes of the returned long hex string should be the peer's MAC address, and equal for all three occurrences.

5.4.2 GSR Series

Do not set a static MAC address on the Port-channel interface. This causes CEF inconsistencies and other assorted failures.Link aggregation and IPv6 do not seem to play well together. Cisco advises against trying this.

Some changes will result in a different MAC address getting chosen for the aggregated link (likely such as reloading a linecard, if it contains the first port in the bundle). This will keep your ports dysfunctional due to port security on the AMS-IX switches and you will have to contact the AMS-IX NOC in such cases to fix this.

Some restrictions apply to what features are supported on link bundles (e.g. sampled NetFlow only on ISE/Engine4+; no uRPF). Also not all line cards support link bundling, and if traffic towards AMS-IX comes in on such an interface you will experience suboptimal load-balancing. Please see the Cisco documentation for more details.

Support for link bundling on Engine 5 linecards will come in 12.0(33)S.Cisco Engineering have a special train called 'Phase 3' (lb-eft-ph3) that is purported to also provide functionality such as MAC address accounting for Port-Channel interfaces. This seems to have been integrated into 12.0(32)S, but IPv6 does not seem to be supported yet.

Below follows a list of Cisco Bug IDs (ddts) related to link aggregation that you need to consider when choosing an appropriate IOS image

CSCee27396
present in 12.0(26)S1; fixed in 12.0(26)S3, 12.0(27)S2, 12.0(28)S1, 12.0(30)SSymptoms: Over 90% CPU usage by CEF Scanner on all linecards and %TFIB-7-SCANSABORTED errors occur when configuring a link bundle. Also, the router sends traffic to MAC addresses taken from its ARP table seemingly at random, instead of to the appropriate next-hop's MAC address.

CSCef12828
present in post-CSCee27396; fixed in 12.0(26)S4, 12.0(27)S3, 12.0(28)S1, 12.0(30)SSymptoms: When traffic passes through a router, the router blocks traffic for certain prefixes behind a port-channel link.

CSCdz33664
present in 12.0(25)S3, 12.0(26)S1, 12.0(27)S2, 12.0(28)S; fixed in 12.0(25)S4Symptoms: An HSRP state change on any Engine2 interface causes a microcode bundle flap on all other Engine2 linecards, preventing load balancing to work due to vanilla microcode getting loaded.

CSCee81071
present in 12.0(26)S3, 12.0(27)S2, 12.0(29)SSymptoms: Router sends Ethernet frames with a source MAC address of beef.f00d.beef and destination MAC address f00d.beef.f00d (which is the pattern scribbled in unallocated memory in linecards), with what looks to be a legitimate payload of transit traffic. This is one of the symptoms of CSCee27396

CSCeb38014
present in 12.0(26)S5; fixed in 12.0(26)S5, 12.0(27)SSymptoms: The BGP Router process flushes the BGP tables for each peer when you change one neighbor's description. This pegs the GRP CPU at 99% for quite a while.

CSCeg31951
present in 12.0(31)S; fixed in 12.0(31)S2 (CSCei53226)
Symptoms: IOS (at least in the PRP code) places each individual public peer in its own update-group if remove-private-as is configured on a peer. Needless to say, this scales badly for a router connected to an Internet exchange. (Try 'show ip bgp replication'.) A collection of hearsay follows for recent IOS images for the GSR PRP regarding link aggregation. AMS-IX does not run any GSRs. Please take this information with appropriately-sized grains of salt.

• 12.0(24)S2 is not advisable (not many specifics known but they include CSCef89562 and CSCee33045)
• 12.0(24)S6 boots but load-balancing is completely off 12.0(25)S until S3 have CSCdz33664
• 12.0(26)S until S4 have CSCef89562, where Engine4+ linecards can have continuously flapping interfaces, but is also somewhat required for Quadra linecards
• 12.0(26)S3 has CSCee27396 integrated but not CSCef12828, which leads to traffic blackholing 12.0(27)S until S3 have CSCef89562 as well
• 12.0.(27)S1 has a problem where it sends traffic to random destinations 12.0(27)S2 has CSCee27396 integrated but not CSCef12828
• 12.0(27)S4 reportedly works reasonably well on PRP2s
• 12.0(28)S1 has problems with Engine2 linecards (CSCef78098) and Engine4+ (CSCef89562)
• 12.0(28)S2 reportedly works better but still sometimes emits beef.f00d.beef frames on normal ports with only an IPv6 address configured
• 12.0(30)S has only been observed to exhibit CSCef12828-like symptoms in conjunction with broken hardware, and also (sometimes) to still emit frames from MAC beef.f00d.beef.
• Routers occasionally still send out frames with beef.f00d.beef as MAC source address on interfaces with an IPv6 but no IPv4 address configured, even on regular links.
• Due to the massive amount of feature requests there will be both a 12.0(32)S and a new 12.0(32)SY train.

You can check for incorrect next-hops by attaching to the linecard and executing show controllers rewrite and show adjacency internal and comparing the two rewrite strings for a certain peer's IPv4 address (suffix the commands with | begin 80.249.20a.b). The first six bytes of the returned long hex string should be the peer's MAC address, and equal for all three occurrences.

Specifying a value is optional, but setting it to the amount of ports in an aggregated link multiplied by 75 is advised.show interfaces Port-channel 1 will display keepalives enabled even though they are not; also, the BIA (burnt-in address, shown as 0000.0000.0000) can be ignored.

Specifying a value is optional, but setting it to the amount of ports in an aggregated link multiplied by 75 is advised.show interfaces Port-channel 1 will display keepalives enabled even though they are not; also, the BIA (burnt-in address, shown as 0000.0000.0000) can be ignored.

5.4.3 CRS (IOS-XR)

5.4.3 CRS (IOS-XR)

IOS supports no bgp fast-external-fallover and event dampening . The no bgp fast external-fallover tells the device to not act immediately on link flaps but to wait for the BGP hold timers to expire before resetting sessions.

Newer versions of Cisco IOS even support ip bgp fast-external-fallover deny in a per-interface context.Note that in practice we have found that the previously advised carrier-delay does not work as expected on Cisco equipment. We suggest you disable fast-external-fallover instead.

In IOS-XR, to disable BGP Fast External Failover globally, add bgp fast-external-failover disable to your global bgp configuration.

IOS supports no bgp fast-external-fallover and event dampening . The no bgp fast external-fallover tells the device to not act immediately on link flaps but to wait for the BGP hold timers to expire before resetting sessions.

Newer versions of Cisco IOS even support ip bgp fast-external-fallover deny in a per-interface context.Note that in practice we have found that the previously advised carrier-delay does not work as expected on Cisco equipment. We suggest you disable fast-external-fallover instead.

In IOS-XR, to disable BGP Fast External Failover globally, add bgp fast-external-failover disable to your global bgp configuration.

Responses on a ICMPv6 multicast listener queries result in bursts of ICMPv6 multicast listener reports. To prevent this configure no ipv6 mld router in interface context. Some other per-interface commands we recommend on a Cisco device:

Responses on a ICMPv6 multicast listener queries result in bursts of ICMPv6 multicast listener reports. To prevent this configure no ipv6 mld router in interface context. Some other per-interface commands we recommend on a Cisco device:

On newer Cisco IOS/IOS-XR versions, the interface IP MTU is automatically set, based on the presence or absence of 802.1q tags. For more details, please consult this document.

On newer Cisco IOS/IOS-XR versions, the interface IP MTU is automatically set, based on the presence or absence of 802.1q tags. For more details, please consult this document.

The configuration fragment below shows how to configure an intermediate L2 switch, which is also part of an EAPS ring. Port 1 is connected to the AMS-IX switch. Ports 2 and 3 are in the ring. The router is somewhere in that ring, in the 'amsix' VLAN.

The configuration fragment below shows how to configure an intermediate L2 switch, which is also part of an EAPS ring. Port 1 is connected to the AMS-IX switch. Ports 2 and 3 are in the ring. The router is somewhere in that ring, in the 'amsix' VLAN.

The configuration fragment below shows the relevant configuration information for a L3-only device. As in the previous example, port 1 is connected to AMS-IX and is configured in the 'amsix' VLAN (untagged).

The configuration fragment below shows the relevant configuration information for a L3-only device. As in the previous example, port 1 is connected to AMS-IX and is configured in the 'amsix' VLAN (untagged).

Force10 E-Series switch/routers support no bgp fast-external-fallover, BGP Graceful Restart, and a link debounce timer to maintain BGP stability during topology switchovers.The recommended option is to use the /link debounce/ command to delay link change notifications on the interface. The default for fiber interfaces is 100 ms, which is a good value to use.

Force10 E-Series switch/routers support no bgp fast-external-fallover, BGP Graceful Restart, and a link debounce timer to maintain BGP stability during topology switchovers.The recommended option is to use the /link debounce/ command to delay link change notifications on the interface. The default for fiber interfaces is 100 ms, which is a good value to use.

On a Foundry BigIron RX, software version < 2.4, we noticed together with a customer that his device had a very aggressive default setting for ICMPv6 ND queries for known MAC addresses. It retransmitted them every second. The retransmit interval can be altered in interface context as follows:

On a Foundry BigIron RX, software version < 2.4, we noticed together with a customer that his device had a very aggressive default setting for ICMPv6 ND queries for known MAC addresses. It retransmitted them every second. The retransmit interval can be altered in interface context as follows:

Note: This command should not be confused with 'ipv6 nd ns-interval', which applies to ND queries for unresolved MAC addresses.

Note: This command should not be confused with 'ipv6 nd ns-interval', which applies to ND queries for unresolved MAC addresses.

BigIron JetCore-based switches support link aggregation only on adjacent ports. The first port must be oddly numbered, and the other port must directly follow the first one. The same goes for any additional pairs of ports in an aggregated link.

CAUTION: On BigIron 15000 switches you cannot build trunks with ports on blade 8, or spanning ports on both sides of slot 8!

BigIron JetCore-based switches support link aggregation only on adjacent ports. The first port must be oddly numbered, and the other port must directly follow the first one. The same goes for any additional pairs of ports in an aggregated link.

CAUTION: On BigIron 15000 switches you cannot build trunks with ports on blade 8, or spanning ports on both sides of slot 8!

BigIron RX or NetIron MLX/XMR switches don't have limits to port placement for aggregated links. Ports can be non-adjacent or even distributed over multiple blades. BigIron RX has a limit of 8 ports per aggregated link, NetIron MLX/XMR raise this to 16 in software 3.5.0, 32 in 3.8.0

BigIron RX or NetIron MLX/XMR switches don't have limits to port placement for aggregated links. Ports can be non-adjacent or even distributed over multiple blades. BigIron RX has a limit of 8 ports per aggregated link, NetIron MLX/XMR raise this to 16 in software 3.5.0, 32 in 3.8.0

As of RX software release 2.5.0 and MLX/XMR software release 3.9.0 the link aggregation syntax changed. The configuration now looks like:

As of RX software release 2.5.0 and MLX/XMR software release 3.9.0 the link aggregation syntax changed. The configuration now looks like:

The primary-port is used as a single point of configuration. All configuration changes to the primary-port are propagated to the other ports in the lag group.

The keyword 'static' designates a standard aggregated link. For an LACP-enabled link, use:

The primary-port is used as a single point of configuration. All configuration changes to the primary-port are propagated to the other ports in the lag group.

The keyword 'static' designates a standard aggregated link. For an LACP-enabled link, use:

We recommend setting the LACP timeout to 'short' to reduce the service interruption time during photonic failovers.

We recommend setting the LACP timeout to 'short' to reduce the service interruption time during photonic failovers.

Foundry/Brocade supports a feature called BGP Graceful Restart that, if all peers support it, will reduce the impact of prefix flaps but the CPU will still have to re-establish any flapped BGP session before the configured interval passes.The command delay-link-event can make the router ignore short link flaps (for example, in the case of a photonic switch swap). We recommend setting this to 20 which equals to 1000 msecs. Consequently, the flap will be logged in syslog, but higher level protocols (BGP in this case) will be unaffected. We suggest to leave fast-external-fallover in its default state.

Foundry/Brocade supports a feature called BGP Graceful Restart that, if all peers support it, will reduce the impact of prefix flaps but the CPU will still have to re-establish any flapped BGP session before the configured interval passes.The command delay-link-event can make the router ignore short link flaps (for example, in the case of a photonic switch swap). We recommend setting this to 20 which equals to 1000 msecs. Consequently, the flap will be logged in syslog, but higher level protocols (BGP in this case) will be unaffected. We suggest to leave fast-external-fallover in its default state.

Make sure to exchange only unicast routes in the unicast ISP peering LAN by explicitly adding the following statement to ,em>all neighbors, groups and prefix-limits:

Make sure to exchange only unicast routes in the unicast ISP peering LAN by explicitly adding the following statement to ,em>all neighbors, groups and prefix-limits:

Be thorough with family inet unicast

If even one of the neighbours, groups or prefix-limits is defined with a family inet "any", you'll enable multicast and turn on MBGP.

Be thorough with family inet unicast

If even one of the neighbours, groups or prefix-limits is defined with a family inet "any", you'll enable multicast and turn on MBGP.

Increasing interface hold-time (1200ms) to preserve BGP sessions during 10/100GE interface swapping

AMS-IX connects 10/100GE members via photonic switch (Glimmerglass), so we can redirect optic signal to our primary and backup switch in case of failure or for maintenance. The signal redirect takes around 20ms, enough to trigger port state change advertisement within the router; because of this, BGP sessions will be torn down as the result. Therefore, we recommend to configure a higher hold-time value on 10/100GE interface to preserve BGP sessions during interface swapping.

Increasing interface hold-time (141809ms) to preserve BGP sessions during 10/100GE interface swapping

AMS-IX connects 10/100GE members via photonic switch (Glimmerglass), so we can redirect optic signal to our primary and backup switch in case of failure or for maintenance. The signal redirect takes around 20ms, enough to trigger port state change advertisement within the router; because of this, BGP sessions will be torn down as the result. Therefore, we recommend to configure a higher hold-time value on 10/100GE interface to preserve BGP sessions during interface swapping.

Juniper's default ARP cache timeout is 20 minutes (by comparison: Cisco's default ARP cache timeout is 4 hours, which fits AMS-IX's relatively static environment much better).

To reduce the amount of unnecessary broadcast traffic, we recommend setting the ARP cache timeout on Juniper routers to 4 hours. A recipe for this follows:

Juniper's default ARP cache timeout is 20 minutes (by comparison: Cisco's default ARP cache timeout is 4 hours, which fits AMS-IX's relatively static environment much better).

To reduce the amount of unnecessary broadcast traffic, we recommend setting the ARP cache timeout on Juniper routers to 4 hours. A recipe for this follows:

Since Junos 9.4 the ARP cache timeout is also configurable on an interface level:

Since Junos 9.4 the ARP cache timeout is also configurable on an interface level:

and on more recent versions of Junos that syntax has changed to:

and on more recent versions of Junos that syntax has changed to:

10.3.1 M-Series

We have encountered no issues with aggregated links and Jun OS (M40, M160, T320). Junos releases prior to 6.0 required VLAN tagging on aggregated interfaces. This limitation has since been removed. An example configuration follows:

10.3.1 M-Series

We have encountered no issues with aggregated links and Jun OS (M40, M160, T320). Junos releases prior to 6.0 required VLAN tagging on aggregated interfaces. This limitation has since been removed. An example configuration follows:

Additionally and optionally you can configure more granular load balancing:

Additionally and optionally you can configure more granular load balancing:

In case that is not granular enough, you can modify the hash-key algorithm with some undocumented options in Junos OS 7.x and up:

In case that is not granular enough, you can modify the hash-key algorithm with some undocumented options in Junos OS 7.x and up:

Also, you can set your aggregated min-links to a value that will cause the bundle to drop in the event that your links can no longer support the amount of traffic you plan on shoving down the pipe. Thus, 2-port aggregated link, pushing 1.2 Gbps sustained across, drop bundle if n == 1;

Also, you can set your aggregated min-links to a value that will cause the bundle to drop in the event that your links can no longer support the amount of traffic you plan on shoving down the pipe. Thus, 2-port aggregated link, pushing 1.2 Gbps sustained across, drop bundle if n == 1;

In a situation with load-balancing over multiple IP interfaces (not AMS-IX), the final statement will make traceroute more confusing to novices as packets may seem to 'bounce' between interfaces by also including TCP/UDP port numbers and ICMP checksums in the algorithm.On an IP1 load-balance per-packet really means per-packet; on an IP2 it actually works per flow, which is preferable.

In a situation with load-balancing over multiple IP interfaces (not AMS-IX), the final statement will make traceroute more confusing to novices as packets may seem to 'bounce' between interfaces by also including TCP/UDP port numbers and ICMP checksums in the algorithm.On an IP1 load-balance per-packet really means per-packet; on an IP2 it actually works per flow, which is preferable.

The link flap introduced by the PXCs make that you have to damp interface transitions. Junos supports a configurable hold-time . A good value would be 1200 ms.

The link flap introduced by the PXCs make that you have to damp interface transitions. Junos supports a configurable hold-time . A good value would be 141809 ms.

Aggregated interfaces require hold timers on all physical interfaces and on the logical aggregated interface. Respectively xe-0/1/0 and ae0 in the example below:

Aggregated interfaces require hold timers on all physical interfaces and on the logical aggregated interface. Respectively xe-0/1/0 and ae0 in the example below:

The configured MTU should be 1514 (this includes Ethernet headers but not the FCS), or 1518 when tagged.

The configured MTU should be 1514 (this includes Ethernet headers but not the FCS), or 1518 when tagged.

Configure the interface facing the Peering LAN as a routed port, disable IPv6 router advertisements and disable LLDP:

Configure the interface facing the Peering LAN as a routed port, disable IPv6 router advertisements and disable LLDP:

If you do decide to configure the port as a switched port with a VLAN-interface, make sure STP is disabled:

If you do decide to configure the port as a switched port with a VLAN-interface, make sure STP is disabled:

To ignore short link-flaps, configure the link-debounce setting:

To ignore short link-flaps, configure the link-debounce setting:

To create an LACP-bundle, configure the ports in a channel-group. This will create a virtual port-channel interface on which you configure the Peering LAN IP address and other settings:

To create an LACP-bundle, configure the ports in a channel-group. This will create a virtual port-channel interface on which you configure the Peering LAN IP address and other settings:

The default ARP timeout on Arista is 4 hours, which is acceptable for the Peering LAN. Should you wish to change it, you can do so as follows:

The default ARP timeout on Arista is 4 hours, which is acceptable for the Peering LAN. Should you wish to change it, you can do so as follows:

The Linux approach to IP addresses is that they belong to the system, not any single interface. As a result, Linux hosts have a default behaviour that is different from most other systems: interfaces semi-promiscuously answer for all IP addresses of all other interfaces. Example:

The Linux approach to IP addresses is that they belong to the system, not any single interface. As a result, Linux hosts have a default behaviour that is different from most other systems: interfaces semi-promiscuously answer for all IP addresses of all other interfaces. Example:

In this example, host tuxco is a Linux box with a peering connection on eth0 (192.168.1.1/24) and a backbone link on eth1 (10.0.0.1/24).When host kannix (192.168.1.2) sends an ARP query for 10.0.0.1 it will get a reply from tuxco's eth0 interface!

In other words, a Linux host will answer to ARP queries coming in on any interface if the queried address is configured on any of its interfaces. The idea behind this is that an IP address belongs to the system, not just to a single interface. Although this may work well for server or desktop systems, it is not desirable behaviour in a router system. One reason is that it is a limited version of proxy-arp, which is forbidden on the AMS-IX peering LAN. Another reason is that two separate routers could potentially answer ARP queries for the same RFC1918 address.

12.1.1 Fixing ARP

The ARP behaviour can be fixed by using arp_ignore and arp_announce on the WAN interface:

In this example, host tuxco is a Linux box with a peering connection on eth0 (192.168.1.1/24) and a backbone link on eth1 (10.0.0.1/24).When host kannix (192.168.1.2) sends an ARP query for 10.0.0.1 it will get a reply from tuxco's eth0 interface!

In other words, a Linux host will answer to ARP queries coming in on any interface if the queried address is configured on any of its interfaces. The idea behind this is that an IP address belongs to the system, not just to a single interface. Although this may work well for server or desktop systems, it is not desirable behaviour in a router system. One reason is that it is a limited version of proxy-arp, which is forbidden on the AMS-IX peering LAN. Another reason is that two separate routers could potentially answer ARP queries for the same RFC1918 address.

12.1.1 Fixing ARP

The ARP behaviour can be fixed by using arp_ignore and arp_announce on the WAN interface:

12.1.2 Multiple Interfaces on One Subnet

If you have multiple interfaces on the same subnet, you may also want to enable arp_filter:

This prevents the ARP entry for an interface to fluctuate between two or more MAC addresses. However, you need to use source routing to make this work correctly. From the Documentation/networking/ip-sysctl-2.6.txt file in the kernel source:

[...]

arp_filter - BOOLEAN

1 - Allows you to have multiple network interfaces on the same subnet, and have the ARPs for each interface be answered based on whether or not the kernel would route a packet from the ARP'd IP out that interface (therefore you must use source based routing for this to work). In other words it allows control of which cards (usually 1) will respond to an arp request.

[...]

12.1.2 Multiple Interfaces on One Subnet

If you have multiple interfaces on the same subnet, you may also want to enable arp_filter:

This prevents the ARP entry for an interface to fluctuate between two or more MAC addresses. However, you need to use source routing to make this work correctly. From the Documentation/networking/ip-sysctl-2.6.txt file in the kernel source:

[...]

arp_filter - BOOLEAN

1 - Allows you to have multiple network interfaces on the same subnet, and have the ARPs for each interface be answered based on whether or not the kernel would route a packet from the ARP'd IP out that interface (therefore you must use source based routing for this to work). In other words it allows control of which cards (usually 1) will respond to an arp request.

[...]

The ARP cache timeout on Linux-based routers should be changed from the default, especially if you have a large number of peers. This parameter can be tuned by setting the appropriate procfs variable through the*sysctl* interface. The Linux arp(7) manual says:

[...]

SYSCTLS

ARP supports a sysctl interface to configure parameters on a global or per-interface basis. The sysctls can be accessed by reading or writing the /proc/sys/net/ipv4/neigh/*/* files or with the *sysctl*(2) interface. Each interface in the system has its own directory in /proc/sys/net/ipv4/neigh/. The setting in the default directory is used for all newly created devices. Unless otherwise specified time related sysctls are specified in seconds.

[...]

base_reachable_time

Once a neighbour has been found, the entry is considered to be valid for at least a random value between base_reachable_time/2 and 3*base_reachable_time/2. An entry's validity will be extended if it receives positive feedback from higher level protocols. Defaults to 30 seconds.

This means that Linux systems keep ARP entries in their cache for some time between 15 and 45 seconds (and yes, the average works out to 3 seconds). This is not very high. In fact, it is lower than the typical BGP keepalive interval and may thus result in excessive ARPs.

We suggest a timeout of at least two hours for ARP entries on your AMS-IX interface, so you'd have to set the base_reachable_time to 2 x 2hrs = 4 hours.

The ARP cache timeout on Linux-based routers should be changed from the default, especially if you have a large number of peers. This parameter can be tuned by setting the appropriate procfs variable through the*sysctl* interface. The Linux arp(7) manual says:

[...]

SYSCTLS

ARP supports a sysctl interface to configure parameters on a global or per-interface basis. The sysctls can be accessed by reading or writing the /proc/sys/net/ipv4/neigh/*/* files or with the *sysctl*(2) interface. Each interface in the system has its own directory in /proc/sys/net/ipv4/neigh/. The setting in the default directory is used for all newly created devices. Unless otherwise specified time related sysctls are specified in seconds.

[...]

base_reachable_time

Once a neighbour has been found, the entry is considered to be valid for at least a random value between base_reachable_time/2 and 3*base_reachable_time/2. An entry's validity will be extended if it receives positive feedback from higher level protocols. Defaults to 30 seconds.

This means that Linux systems keep ARP entries in their cache for some time between 15 and 45 seconds (and yes, the average works out to 3 seconds). This is not very high. In fact, it is lower than the typical BGP keepalive interval and may thus result in excessive ARPs.

We suggest a timeout of at least two hours for ARP entries on your AMS-IX interface, so you'd have to set the base_reachable_time to 2 x 2hrs = 4 hours.

The above command tells you that the ARP cache timeout is 30 seconds average. To change it so it's between 2 and 6 hours, use the following command:

The above command tells you that the ARP cache timeout is 30 seconds average. To change it so it's between 2 and 6 hours, use the following command:

Here ifname is the name of the interface that connects to AMS-IX. You can also use "default" here, but that may have undesired side-effects for your other interfaces.

Here ifname is the name of the interface that connects to AMS-IX. You can also use "default" here, but that may have undesired side-effects for your other interfaces.

As with the IPv4 ARP cache, Linux systems tend to set the lifetime of the IPv6 neighbor cache quite short as well. The lifetime is controlled in a similar way as for IPv4 ARP.

As with the IPv4 ARP cache, Linux systems tend to set the lifetime of the IPv6 neighbor cache quite short as well. The lifetime is controlled in a similar way as for IPv4 ARP.

Disable proxy-arp using sysctl:

Disable proxy-arp using sysctl:

IPv6 stateless autoconfiguration must be disabled:

IPv6 stateless autoconfiguration must be disabled:

You may need to turn off the Reverse Path Filter (rp_filter) functionality on a Linux-based router to allow asymmetric routing, particularly on your WAN interface.To disable the RP filter:

You may need to turn off the Reverse Path Filter (rp_filter) functionality on a Linux-based router to allow asymmetric routing, particularly on your WAN interface.To disable the RP filter:

The various system parameters discussed above can be set at boot time by adding it to a file such as /etc/sysctl.conf. The exact name, location and very existence of this file typically depends on the Linux distribution in use, but both Debian and Red Hat/Fedora use /etc/sysctl.conf:

The various system parameters discussed above can be set at boot time by adding it to a file such as /etc/sysctl.conf. The exact name, location and very existence of this file typically depends on the Linux distribution in use, but both Debian and Red Hat/Fedora use /etc/sysctl.conf:

CAUTION: Modules must be loaded before sysctl is executed

On Debian systems, kernel modules for some network interfaces (e.g. 10GE cards) are not loaded before the init process executes the script thatruns the sysctl commands. In those cases, it is necessary to force the module to be loaded earlier. The same goes for the IPv6 settings; the ipv6 module is usually not loaded until the network interfaces are brought up, which is typically after the sysctl variables are set by the procps.sh script.(On Red Hat/Fedora systems no action needs to be taken; the /etc/init.d/network script automatically (re-)sets the sysctl variables before and after bringing up the interfaces.)There are a few ways around this:

On Debian-based systems, this can be done by creating a symbolic link in /etc/rc2.d to re-run procps.sh after the network is brought up:

CAUTION: Modules must be loaded before sysctl is executed

On Debian systems, kernel modules for some network interfaces (e.g. 10GE cards) are not loaded before the init process executes the script thatruns the sysctl commands. In those cases, it is necessary to force the module to be loaded earlier. The same goes for the IPv6 settings; the ipv6 module is usually not loaded until the network interfaces are brought up, which is typically after the sysctl variables are set by the procps.sh script.(On Red Hat/Fedora systems no action needs to be taken; the /etc/init.d/network script automatically (re-)sets the sysctl variables before and after bringing up the interfaces.)There are a few ways around this:

On Debian-based systems, this can be done by creating a symbolic link in /etc/rc2.d to re-run procps.sh after the network is brought up:

Enable bonding driver support in the kernel (CONFIG_BONDING=m)Edit /etc/modules to load the bonding driver on boot:

Enable bonding driver support in the kernel (CONFIG_BONDING=m)Edit /etc/modules to load the bonding driver on boot:

The miimon parameter specifies the frequency for link-monitoring, measured in ms.Install the ifenslave package (apt-get install ifenslave). This package provides the /sbin/ifenslave tool, which is used to attach physical interfaces to the bonding interface.Add the bonding interface to /etc/network/interfaces:

The miimon parameter specifies the frequency for link-monitoring, measured in ms.Install the ifenslave package (apt-get install ifenslave). This package provides the /sbin/ifenslave tool, which is used to attach physical interfaces to the bonding interface.Add the bonding interface to /etc/network/interfaces:

The above example creates a bonding interface with two physical interfaces.For more information see the file Documentation/networking/bonding.txt in the kernel source tree.

The above example creates a bonding interface with two physical interfaces.For more information see the file Documentation/networking/bonding.txt in the kernel source tree.

Modern kernels have MLDv2 on by default and there is no sysctl parameter to switch it off. The only known way by now is to drop it with an outgoing filter:

Modern kernels have MLDv2 on by default and there is no sysctl parameter to switch it off. The only known way by now is to drop it with an outgoing filter:

• Port configuration

• Port configuration

• LAG configuration
  Mode, MTU, Slave port and comment:

• LAG configuration
  Mode, MTU, Slave port and comment:

• IP Configuration

• IP Configuration

By default Mikrotik routers have their own proprietary Mikrotik Discovery Protocol and CDP enabled. To turn these discovery protocols off, in the Web UI go to IP > Neighbors > Discovery Interfaces and disable the protocols on the AMS-IX-facing interface.

• Bridge port disabled
  Confirm that the ports facing AMS-IX are not included in the bridge. This includes disabling STP on the port.

By default Mikrotik routers have their own proprietary Mikrotik Discovery Protocol and CDP enabled. To turn these discovery protocols off, in the Web UI go to IP > Neighbors > Discovery Interfaces and disable the protocols on the AMS-IX-facing interface.

• Bridge port disabled
  Confirm that the ports facing AMS-IX are not included in the bridge. This includes disabling STP on the port.

• CDP, LLDP, MNDP

• CDP, LLDP, MNDP

• OSPF
  Please confirm that the interface facing AMS-IX is not included in the OSPF instance.
  If so, please remove it from the OSPF.

• OSPF
  Please confirm that the interface facing AMS-IX is not included in the OSPF instance.
  If so, please remove it from the OSPF.

• RIP
  Please confirm that the interface facing AMS-IX is not included in the OSPF instance. If so, please remove it from the RIP.
  (Similarly, please check the configuration for EIGRP and IS-IS.)

• RIP
  Please confirm that the interface facing AMS-IX is not included in the OSPF instance. If so, please remove it from the RIP.
  (Similarly, please check the configuration for EIGRP and IS-IS.)

• IGMP
  The port facing AMS-IX must not be included in the IGMP process. Please check that IGMP is disabled.

• IGMP
  The port facing AMS-IX must not be included in the IGMP process. Please check that IGMP is disabled.

• DHCP
  The port facing AMS-IX must not be included in the DHCP process.

• DHCP
  The port facing AMS-IX must not be included in the DHCP process.

• Proxy-ARP
  It must be disabled:

• Proxy-ARP
  It must be disabled:

• IPv6 ND

• IPv6 ND

The below CLI configuration details the basic BGP configuration to establish an IPv4 BGP session towards one of our Route Servers. The customer can use a similar approach for IPv6:

The below CLI configuration details the basic BGP configuration to establish an IPv4 BGP session towards one of our Route Servers. The customer can use a similar approach for IPv6:

• BGP Policies/Filters
  Following the path, /routing/filter/rule the customers will be able to create different filters according to their needs. As shown in the command above, this filter can be applied either to input.filter= or output.filter-chain=. More information about Mikrotik filters can be found here.

• BGP Policies/Filters
  Following the path, /routing/filter/rule the customers will be able to create different filters according to their needs. As shown in the command above, this filter can be applied either to input.filter= or output.filter-chain=. More information about Mikrotik filters can be found here.

Here, ifname refers to your interface towards AMS-IX, or the string 'all'

Here, ifname refers to your interface towards AMS-IX, or the string 'all'