[c-nsp] Showing alternate BGP paths

[Karol Mares]

Hi Oli,

I thought , that the new feature bgp dmzlink-bw, is used for this
purpose.
As i can see, both load-balanced routes are propagate through the
IBGP/EBGP path.


lab# show ip bgp 10.1.1.0
BGP routing table entry for 10.1.1.0/24, version 48
Paths: (2 available, best #2)
Multipath: eBGP
  Advertised to update-groups:
     1          2
  200
    172.16.1.1 from 172.16.1.2 (10.1.1.1)
      Origin incomplete, metric 0, localpref 110, valid, external,
multipath, best
      Extended Community: 0x0:0:0
      DMZ-Link Bw 512 kbytes
  200
    172.16.2.2 from 172.16.2.2 (10.1.1.1)
      Origin incomplete, metric 0, localpref 110, valid, external,
multipath, best
      Extended Community: 0x0:0:0
      DMZ-Link Bw 625 kbytes 

The output shows that a route for each exit link on lab router  to
autonomous system 200 has been installed as a best path i
n the BGP routing table.

                   iso

On Thu, 2006-09-14 at 09:36 +0200, Oliver Boehmer (oboehmer) wrote:
> cisco-nsp-bounces at puck.nether.net <> wrote on :
> 
> > Hi,
> >     We have a setup with 3 routers running BGP connecting to
> > our upstream
> > provider and iBGP with the other routers on our local
> > network. Usually, when
> > the "sh ip bgp xxx.xxx.xxx", is used we can see:
> > 
> > - the best path
> > - other alternative paths with the same local preference
> > 
> > Is it possible to also view paths with less local preference
> > and inactive routes? At the moment we have to run the command on the
> router that is
> > directly connected to a certain upstream (eBGP) to view
> > available paths from them which we can't see from our iBGP routers.
> Thanks.
> 
> No, BGP only sends the best path to its peers, so if you receive
> multiple paths from eBGP peers, the knowledge of the non-best-path is
> limited to these nodes.
> 
> There are some efforts to change the BGP protocol to send multiple paths
> (essentially to allow load-balancing), but this has not been finalized
> and implemented anywhere yet (as far as I know)..
> 
> 	oli
> 
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