Advertisement of Equinix Chicago IX Subnet

[johnstong at westmancom.com (Graham Johnston)]

This afternoon at around 12:17 central time today we began learning the subnet for the Equinix IX in Chicago via a transit provider; we are on the IX as well. The subnet in question is 208.115.136.0/23. Using stat.ripe.net I can see that this subnet is also being learned by others, see the snip below. On our network this caused a nasty routing loop until we figured out what was wrong. My current best understanding is that because the route was learned via eBGP it trumped the OSPF learned route. As soon as I filtered the advertisement from my transit provider everything returned to normal. What am I doing that isnâ??t best practices that would have prevented this?

Thanks,
graham


RIPE Info
1 RRCs see 1 peers announcing 208.115.136.0/23 originated by AS32703<https://stat.ripe.net/AS32703>

*         â?¼RRC00 in Amsterdam, Netherlands sees 1 ASN orginating 208.115.136.0/23.AS32703

o    â?¼AS32703<https://stat.ripe.net/AS32703> is seen as the origin by 1 peer.192.102.254.1

§  �192.102.254.1<https://stat.ripe.net/192.102.254.1> is announcing route AS395152<https://stat.ripe.net/AS395152> AS63297<https://stat.ripe.net/AS63297> AS6327<https://stat.ripe.net/AS6327> AS36280<https://stat.ripe.net/AS36280>AS32703<https://stat.ripe.net/AS32703>.

§  Origin: IGP

§  Next Hop: 192.102.254.1

§  Peer: 192.102.254.1

§  Community: 63297:1000

§  AS Path: 395152 63297 6327 36280 32703

§  Last Updated: 2019-03-27T17:17:19


Route-views
route-views.chicago.routeviews.org> show ip bgp 208.115.136.0
BGP routing table entry for 208.115.136.0/23
Paths: (1 available, best #1, table Default-IP-Routing-Table)
  Not advertised to any peer
  32709 32703
    208.115.136.134 from 208.115.136.134 (63.134.128.248)
      Origin IGP, localpref 100, valid, external, best
      AddPath ID: RX 0, TX 64414249
      Last update: Wed Mar 27 17:16:09 2019
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