Advertisement of Equinix Chicago IX Subnet

[nick at foobar.org (Nick Hilliard)]

Graham Johnston wrote on 27/03/2019 21:36:
> What am I doing that isnâ??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