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I'm looking to use BIRD or similar to advertise a route from a linux box sitting on 169.254.0.3 (on a /28 for eg) to the router at 169.254.0.1 (Which happens to be AWS).

The route advertised to AWS needs to be the following;

AWS Subnet (10.0.0.0/24) -> GW 169.254.0.1

Where 169.254.0.1 is a firewall. Can I magic one of these to advertise a different gateway for a network?

Thanks!

Alex Turner
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1 Answers1

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Routing protocols, like BGP, don't advertise gateways. A gateway is a host concept. When a routing protocol advertises a prefix, it is saying to the other routers with which it shares the routing protocol, "I know how to get to this network, so you can send traffic destined for it to me."

BGP advertises prefixes to peer BGP speakers, either within the same AS (iBGP) or in a different AS (eBGP). Within the same AS, one BGP router cannot advertise a prefix learned from another iBGP speaker. This means that iBGP needs to have a full mesh within the AS, or it needs to use a mitigation such as Route Reflectors or Confederations.

Ron Maupin
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  • Thanks Ron. I understand that, but in this instance I'm looking to use BGP more like an API to the other router's route table. We're trying to peer AWS with a third party who doesn't support BGP so we're trying to `spoof` BGP somehow. My question is more so - can you use a linux daemon to statically update NEXT_HOP on a peer router? – Alex Turner Jan 18 '16 at 06:22
  • Each router makes its own routing decisions given the available information. With BGP, the there are multiple ways to try to influence a neighbor to send traffic to you (lower MED) or away from you (AS_Path prepending), but that doesn't guarantee anything. You simply cannot tell a neighbor to use a a particular router as the next hop. If the third party isn't peering with your routing protocol, you have no chance of influencing how it routes traffic. – Ron Maupin Jan 18 '16 at 06:36