IPv4 ARP / IPv6 Neighbor Timeout
Each equipment vendor implements its own maximum ages for the IPv4 ARP and IPv6 neighbour caches. The values vary widely and in at least one case (Linux) are not a constant.
Low ARP timeouts can lead to excessive ARP traffic, especially if the values are lower than the BGP KEEPALIVE interval timers. However, long timeouts can theoretically lead to longer downtime if you change equipment (your peers will 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.
Peering LAN Prefix
The following prefixes are used by the ECIX peering LANs and are part of AS9033 which means that these are not supposed to be globally routable:
- Frankfurt am Main
Do not configure "network 18.104.22.168/24" or any of the other peering LANs in your router's BGP configuration.
Do not redistribute the route, a supernet, or a more specific outside of your AS. We (AS9033) announce it with a no-export attribute, please honor it.
In short, you can take the view that the Peering LANs are 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 Peering LANs. Exchanging multicast routes is useless since multicast traffic is not allowed on the (unicast) Peering LANs.