[c-nsp] BGP Route selection

[Brian Turnbow]

Setting the metric is not going to affect your BGP route selection.
On router A you can set the weight
Or on router 2 you can  prepend an AS.(you could have used local preference if the as was the same)
Check out 
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094431.shtml
On how BGP selects paths


Regards
Brian
 

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Gary Roberton
Sent: venerdì 23 maggio 2008 16.09
To: Pete Templin
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] BGP Route selection

All

The network in question is actually 90.0.0.0.  All routers are in their own
separate AS.  The route in question is a connected network not
redistributed.

To make it clearer;
Router X has network 90.0.0.0 connected
Router X advertises to both Router1 and Router2.
Router 1 sends it on to Router A
Router 2 has a route map that does 'set metric 50' and then passes it onto
RouterA.
We want RouterA to go via Router1 whenever Router1 is up

Router A BGP table entry is shown here;

*  90.0.0.0         10.40.1.6               50             0 64604 1000 i

*>                  10.40.1.2                              0 64603 1000 i

Router A puts 10.40.1.2 route into global routing table
Router1 goes down
Router A puts 10.40.1.6 route into global routing table
Router1 comes up
RouterA puts entry back in BGP table but leaves route in global table alone.

Any help appreciated.






On Fri, May 23, 2008 at 1:20 PM, Pete Templin <petelists at templin.org> wrote:

> Gary Roberton wrote:
>
>  I have router A receiving network 80.0.0.0 from router 1 and router 2.
>> Router 2 weights its metric so that it is less favourable.
>>
>
> Are routers 1 and 2 in your AS, or in another AS?  Also, please clarify
> 'weights its metric' - do you mean it adjusts weight, it adjusts metric, it
> adjusts origin, etc.?
>
>  In router A's BGP table I can see both routes and the route from Router 1
>> is
>> placed in the global routing table.  Fine.
>>
>
> Are you seeing the various BGP knobs showing the settings you'd expect from
> above?
>
>  When you turn off Router1, Router A removes the route from the routing
>> table
>> and installs the less favoured route from Router2.  What you would expect.
>>
>> When I turn on Router1, Router A does not put the better route back into
>> the
>> routing table, even though it sees both in its BGP table.
>>
>
> Are you seeing the various BGP knobs showing the settings you'd expect from
> above?
>
> pt
>
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