Advertisement of Equinix Chicago IX Subnet

Wed Mar 27 21:52:33 UTC 2019

Thank you Nick.

Graham Johnston
Manager, Network Services
Westman Communications Group
1906 Park Avenue | Brandon, MB | R7B 0R9
204-717-2829 |    
johnstong at westmancom.com

-----Original Message-----
From: Nick Hilliard <nick at foobar.org> 
Sent: March 27, 2019 4:50 PM
To: Graham Johnston <johnstong at westmancom.com>
Cc: nanog at nanog.org
Subject: Re: Advertisement of Equinix Chicago IX Subnet

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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