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Re: OpenBGP: aggregating routes / set neighbor next-hop



On Tue, Apr 04, 2006 at 11:46:24AM +0100, tony sarendal wrote:
> On 04/04/06, Falk Brockerhoff <fb_(_at_)_smartterra_(_dot_)_de> wrote:
> >
> > Am 29.03.2006 um 14:32 schrieb Falk Brockerhoff:
> >
> > >> that, again, is sth nobody ever asked for or missed :)
> > >> however, the (completely untested except for compilation) diff below
> > >> should add "set nexthop self".
> > >
> > > Ui, you're realy fast :-) Thank you for your quick response. I'll
> > > compile this and test it with a spare old Cisco-Router as
> > > "Development-Core" next weekend. I'll give you a feedback about it.
> >
> > The next-hop patch is working perfectly, thanks!
> >
> > But I've got another problem: actually I'm announcing the following
> > prefixes from a "testing core"-router to the border-router running
> > openBGPd:
> >
> > Dest/mask          Next-Hop         Med      LocalPref
> > 192.168.0.0/24     10.0.0.6    ---          100
> > 192.168.0.0/29   10.0.0.6   ---          100
> > 10.0.0.4/30   10.0.0.6  ---          100
> > 192.168.1.153/32 10.0.0.6    ---          100
> >
> > - 192.168.0.0/24 is an aggregated prefix, caused by 192.168.0.1/29.
> > - 10.0.0.4/30 is from the transfer-network between my core (10.0.0.6)
> > and the openbgpd-router (10.0.0.5).
> > - 192.168.1.153/32 is the loopback-address of the core.
> >
> > In the openbgpd.conf I configured "network 192.168.0.0/24". This
> > prefix is correctly announced by openbgpd to my external neighbor.
> > But on my open BGPd-router I can't ping the address 192.168.0.1,
> > which is configured on a interface at the core-router:
> >
> > $ ping 192.168.0.1
> > PING 192.168.0.1 (192.168.0.1): 56 data bytes
> > ping: sendto: No route to host
> > ping: wrote 192.168.0.1 64 chars, ret=-1
> >
> >
> > $ bgpctl sh rib 192.168.0.1
> > flags: * = Valid, > = Selected, I = via IBGP, A = Announced
> > origin: i = IGP, e = EGP, ? = Incomplete
> >
> > flags destination         gateway          lpref   med aspath origin
> > AI*>  192.168.0.0/24    0.0.0.0            100     0 i
> > I*    192.168.0.0/24    10.0.0.6      100     0 i
> >
> > Any idea, what's going on here?
> >
> > my bgpd.conf:
> >
> > AS 64400
> > router-id 192.168.1.150
> > network 192.168.0.0/24
> 
> 
> Why do you have network 192.168.0.0/24 in bgpd.conf if you already get
> that prefix from the core router ?
> 
> Above you could see 192.168.0.0/24 from the core router and the local box,
> the local /24 was chosen as best path.
> 
> Some pure guess work here:
> Do you have a /24 network statement in your bgpd.conf but no real route
> for it ?  Maybe this in bgpd means that you will announce that /24,
> basically beating the /24 you are receiving from the core, and thus not
> installing that /24 into the routing table.
> 

Yes. Announced networks will not install routes in the FIB additionally
they do not need a present route in the FIB (this is different from most
other routing suites).

So you either need to install a static route for 192.168.0.0/24, remove
the "network 192.168.0.0/24" on the border router, twiddle with localpref
to make the core router prefix prefered or use some IGP.

-- 
:wq Claudio



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