iBGP

[fredrik danerklint]

Setup:

Transit <-> CR2 <-> ER2

Loopback addressess:
CR2 has the ip adress of xx.xx.xx.2/32.
ER2 has the ip adress of xx.xx.xx.4/32.

Network link:
CR2 has the ip address xx.xx.xx.201/30
ER2 has the ip address xx.xx.xx.202/30

All announced via ospf so ping and traceroute does work between each other.

bird> show route  for 77.73.232.6 all
77.73.232.0/21     via xx.xx.xx.201 on igb2 [b4_sekkaa_1_cr2 2011-09-30 
22:18:34 from xx.xx.xx.2] * (100/6) [AS42678i]
        Type: BGP unicast univ
        BGP.origin: IGP
        BGP.as_path: 35706 8359 25513 42678
        BGP.next_hop: xx.xx.xx.2
        BGP.med: 0
        BGP.local_pref: 100

$netstat -rn | grep 77.73.232.0/21
77.73.232.0/21     xx.xx.xx.201      UG1         0        0   igb2

protocol bgp b4_sekkaa_1_cr2 
{
    description "sekkaa-1-cr2";
    import filter {
        accept;
    };
    export filter {
        accept;
    };
    
    interpret communities off;
    local as my_as;
    default bgp_med 0;
    default bgp_local_pref 200;
    neighbor xx.xx.xx.2 as 52011;
    source address xx.xx.xx.4;
        start delay time 30;
        next hop self;
        multihop 4;
}

This is from the internal router ER2. 





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> 
> fredrik danerklint wrote:
> > I already have the 'next hop self;' set in both of the routers. still no
> > luck.
> 
> Can you show BGP configuration block on both routers?
> 
> It would be great to see
> 'show route [table XXX] for some_prefix_advertised_by_router1 all' on
> both routers, too
> 
> > 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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-- 
//fredan