Advertisement of Equinix Chicago IX Subnet
Nick Hilliard
nick at foobar.org
Wed Mar 27 21:50:26 UTC 2019
Graham Johnston wrote on 27/03/2019 21:36:
> What am I doing that isn’t best practices that would have prevented this?
you're setting the next-hop of the prefixes learned at the IXP to be
your own IP address from the IXP subnet (i.e. 208.115.136.0/23).
When your routers learn this address from an external source, that is
preferred to your internal OSPF route. Ergo your IX traffic is sent out
via transit.
There are two things you should do:
1. change the bgp distance for ebgp to be higher than all your IGPs. On
a cisco router, you would use something like:
router bgp xxx
address-family ipv4
distance bgp 200 200 200
address-family ipv6
distance bgp 200 200 200
2. use next-hop-self on internal ibgp sessions to ensure that when you
redistribute the eBGP routes learned from your IX towards the internals
of your network, the next-hop address is set to be the loopback address
of your peering router. I.e. you remove the requirement for your
internal network to know anything about the IXP address range.
Nick
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