iBGP

Alexander V. Chernikov melifaro at ipfw.ru
Fri Sep 30 23:44:00 CEST 2011


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fredrik danerklint wrote:
> Hi,
> 
> FreeBSD 8.2 and Bird 1.3.3.
> 
> I do my internal peering between routes on loopback interfaces.
> All the loopback interfaces is announced over ospf.
> 
> To be able to get an bgp session the 'multi hop 4;' is needed.
> 
> The question I have is what value should the 'next hop' be? I would like to 
> have it to the neighbour address of the peering session but it seems it always 
> the nearest physical network interface address (to the neighbour) that's 'next 
> hop'. 
RFC recommendation for IBGP session tells us:

When sending a message to an internal peer, if the route is not
         locally originated, the BGP speaker SHOULD NOT modify the
         NEXT_HOP attribute unless it has been explicitly configured to
         announce its own IP address as the NEXT_HOP
(RFC 4271 clause 5.1.3)

You can alter next hop via 'next hop self' config option. It will set
next hop address to whatever you configure in 'source address' option.

> 
> I did even try with setting bgp_next_hop=10.10.10.11; within the filter of the 
> bgp protocol but that did not work.
> 

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