IPv6 eBGP next_hop

Mathias Wolkert tias at netnod.se
Thu Oct 13 13:03:52 CEST 2011


Hi

I need to alter the next_hop for IPv6 prefixes advertised over IPv6 eBGP.

I'm using a filter that says "bgp_next_hop = x:x:0:1c::1 ;".
And it is seen in the birdc6 with:
show route all <filtername> as

BGP.next_hop: x:x:0:1c::1

but on the line I see:

Next hop: x:x:0:1c::2 (16)		#The GUA of the router
Next hop: fe80::230:48ff:feba:6b17 (16)	#The LL of the router

which also is what I see on the receiving cisco.

Has this behavior changed? i believe I had this working in bird-1.2.5
I'm now running bird-1.3.5 on Debian Lenny.

What I'm really looking for is a way to only send a manually set
globally unique address and no link-local.

When I read the bird docs, it seems odd that this is referred to as a
"improper bgp update".

My interpretation of rfc2545 section 3 is that link-local is optional.

It's not at all clear on how a receiver should treat an update with both
LL and GUA NHs.

My general feeling is that what was simple in IPv4, is not thought
through in IPv6.

/Tias



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