One BGP session flapping but not the other

20 Dec 2017

      Hi,

I have a pretty simple design: two edge routers, one hypevisor. The
routing is done with the help of BGP.
regis is the hypervisor.

  +---------+     +-------+
  | nominoe |     | budic |
  +---------+     +-------+
       \             /
        \           /
         \         /  AS204092
  --------\-------/---------
           \     /    AS65000
          +-------+
          | regis |
          +-------+

The IPv4 session between nominoe and regis is flapping, but not the one
with budic.
The IPv6 sessions are stables.

nominoe and budic are FreeBSD 11.1-RELEASE boxes, running bird 1.6.3
regis is a gentoo box running bird 1.6.3 too

At each time the session is flapping, I can see 'bird: Kernel dropped
some netlink messages, will resync on next scan.' in the logs of regis.

What does that mean, and what part of the configuration is acting on it?

The sessions are configured the same maner at the edge side:
template bgp DOWNSTREAM {
	export all;
	import keep filtered;
}

protocol bgp bgp_alarig from DOWNSTREAM {
	local as 204092;
	description "BGP for alarig";

	neighbor 89.234.186.100 as 65000;
	import keep filtered;
	import filter bgp_filter_customer_alarig_in;
}

And the same goes for the hypervisor:
template bgp UPSTREAM {
	local as myasn;
	# Be able to see filtered routes with "sh route filtered" command
	import keep filtered;

	# Protect ourselves from massive routes leaks
	receive limit 700000 action block;

	# Announce only our IP allocations
	export where proto = "static_alarig_allocations";
	export limit 1 action block;
}

protocol bgp bgp_nominoe from UPSTREAM {
	description "nominoe";
	neighbor 89.234.186.7 as 204092;

	# Local address we use to establish the BGP session
	source address 89.234.186.100;

	# password=''

	# Accept all routes from Cogent except bogons and other bad stuff
	import filter bgp_filter_nominoe_in;
}

protocol bgp bgp_budic from UPSTREAM {
	description "nominoe";
	neighbor 89.234.186.6 as 204092;

	# Local address we use to establish the BGP session
	source address 89.234.186.100;

	# password=''

	# Accept all routes from Cogent except bogons and other bad stuff
	import filter bgp_filter_budic_in;
}

I can paste the rest of the configuration if you think it’s relevant.

Thanks,
-- 
alarig

One BGP session flapping but not the other

Alarig Le Lay