BGP prefix disappearing without reason version 3

RouterOS Forwarding Protocols
1

Hello,

I have a problem with Mikrotik RoS 3 (3.30 and 3.28). Using version 4 ot seems to work fine.
The setup is very simple, I am using BGP to provide fail-over between two directly Mikrotiks.

The problem is that when the Mikrotik version 3 establishes the second BGP session the first BGP
session looses all the prefixes it had for no reason. However on the Mikrotik version 4 it correctly
keeps the prefixes for both sessions.

I have attached a screenshot of both Mikrotik’s.
mik2.png
mik1.png

2

Your bgp-peers use the Same id?

3

Yes they are the same router.

Basically I have two routers with two interfaces, and for each interface there is a BGP session.

Router1 ---- link a ---- Router2
Router1 ---- link b ---- Router2

So I have one BGP session for link A and and another for link B. The BGP configuration is the same (no filters, just redistribute connected) so the prefix count on both session should match.

4

im surprised that even works at all on 4.x. You really should not have 2 duplicate peers. What’s the point anyhow?

5

Its for providing redundancy in case one of either link fails. I know I can do this with other solutions like OSPF or some Mikrotik scripts but:

  1. BGP runs over TCP so no I do not need L2.
  2. Not every CPE or PE is a Mikrotik in my network, BGP is supported by the other vendors.
  3. I need to filter routes based on BGP communities.
6

I would rebuild that a little bit.
create a loopback bridge on each router with a loopback address, and announce the loopback addresses via OSPF.
then set up the BGP peers using the loopback addresses.

Should a link fail, OSPF will converge and route packets the other way, keeping the BGP session alive.