BGP peer advice

RouterOS Forwarding Protocols
1

Hi,

I’m setting up a network with two border routers each connecting to different providers. I think i’m ok with the setup but have one question:

When you peer a BGP router to another local peer on same LAN subnet is it actually necessary to have a dedicated link between the two routers if they are already on the same subnet or can they just talk over the LAN? All the examples show either a VLAN or a dedicated cable linking the two routers?

Thanks.

2

I always like to use a dedicated link wherever possible for several reasons:

  1. If the better route is on a different router than the one traffic was destined for, then you may end up sending the same traffic through the switch twice
  2. Redundancy - the more redundant paths you have the better

It is perfectly valid to peer across a switch for the iBGP peering, it just depends on what your design requirements are.

3

Hi, Thanks for the answer. They can’t really have a dedicated link as they are at opposite ends of a 100km network. could do a VLAN over the link but then it wont really make any difference to bandwidth used, it would just allow the router to think it had a separate interface linking it. Unless there is any specific point in doing that I would save myself the bother setting up VLANS and just let them talk over the network? They would be on same subnet anyway.

4

Because of the distance involved, I might look at putting some QoS rules in to ensure the iBGP link always had priority. If the LAN becomes congested and the peering drops, it could cause interruptions in service.

5

Thanks for the help :slight_smile: