BGP path prepend / route selection

[Alexander Shikov]

Hi,

On Fri, Oct 25, 2013 at 03:56:45PM +0000, Amadeus wrote:
> Dear list,
> can you explain why the following route (0.0.0.0/0) is selected to go via
> as403, as as4057 clearly displays the shortest path here?
> As you can see I have used bgp_path.prepend() 3x on as403 for its own ASN.
> Thanks, Amadeus
> bird> show route for 0.0.0.0/0 table ffc all
> 0.0.0.0/0          via 169.254.40.3 on ffc403 [as403 14:38] * (150)
> [AS403i]
>  Type: BGP unicast univ
>  BGP.origin: IGP
>  BGP.as_path: 403 403 403 403
>  BGP.next_hop: 169.254.40.3
>  BGP.local_pref: 100
>                    via 169.254.40.64 on ffc4064 [as4064 14:32] (100)
> [AS4057i]
>  Type: BGP unicast univ
>  BGP.origin: IGP
>  BGP.as_path: 4064 40120 4057
>  BGP.next_hop: 169.254.40.64
>  BGP.local_pref: 100
>                    via 169.254.40.57 on ffc4057 [as4057 Oct14] (100)
> [AS4057i]
>  Type: BGP unicast univ
>  BGP.origin: IGP
>  BGP.as_path: 4057
>  BGP.next_hop: 169.254.40.57
>  BGP.local_pref: 100

it is because local-pref. Default route to AS403 has higher local-pref 
than one to AS4057.

-- 
Alexander Shikov
Technical Staff, Digital Telecom IX
Tel.: +380 44 201 14 07
http://dtel-ix.net/