[c-nsp] dumb BGP question

[umair saeed]

Hi,

if its matter of egrees from router A. customers usually use local pref to select outgoing ISP. 

Remember the AS_PATH comes after local preference in bgp path selection.

They must be using route-map on neighbor command to change the default local preference of prefixes receiving from different ISPs.Higher local-pref  will determine preferred outgoing path.

However actual path selection can be determined by sh ib bgp prefix command as suggested by others.



Thanks & Best Regards, Umair SaeedAM IP Operations Core South ,
Pakistan Telecommunication Company Ltd,
Phone # +92 333 2354591


> From: scott at granados-llc.net
> To: john at citylinkfiber.com
> Date: Tue, 31 Jan 2012 16:20:55 -0500
> CC: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] dumb BGP question
> 
> Remember that pref is non transitive.
> 
> If you could, could you do a show ip bgp prefix and paste the output?
> 
> Then we might be able to expand more.
> 
> Thanks
> 
> On Jan 31, 2012, at 3:42 PM, John Brown wrote:
> 
> > Hi,
> > I'm suffering from driving spreadsheets instead of routers.
> > 
> > Have a customer that has two routers.
> > 
> > A  and B
> > 
> > A is connected to us
> > B is connected to two other eBGP neighbors (transit providers)
> > 
> > A and B are connected via iBGP.
> > 
> > A == 7300 widget
> > B === 9000 widget
> > 
> > Traffic via our link is nearly 100 percent ingress to their router A.
> > Very little egress from A.
> > 
> > A is basically a router that feeds the link to us.
> > 
> > B is their main "core" router.
> > 
> > Looking at the routes in B, it shows that they are pref'n routes via B's transit providers, instead of via our link through A.
> > 
> > Yet the AS path is much shorter via A to us.
> > 
> > The same route via B is 5 AS's (no padded) and the route via A is 2 AS's
> > 
> > In looking at the route selection priorities, Local-Pref and then AS path should cause our routes to win well before the iBGP / eBGP selection rule(S)
> > 
> > Not sure what I'm missing here. I know its gotta be dumb and in another life I would know the answer.
> > 
> > Thoughts oh wise list ??
> > 
> > Mucho thanks.
> > 
> > 
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> 
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