[c-nsp] Preloading AS to static network entry via route-map: Duh?

[Harold Ritter]

Hi Elmar,

This is not supported as this could break the following requirement from section 5.1.2 of RFC4172 if you were to send the prefixes generated via the network statement to an iBGP neighbor.

  b) the originating speaker includes an empty AS_PATH attribute in
         all UPDATE messages sent to internal peers.  (An empty AS_PATH
         attribute is one whose length field contains the value zero).

The way to do what you want is to mark the prefix with a given community using the route-map on the network statement and later perform the as-path prepend for that same community via an outbound route-map. It would something like this:

router bgp 65001
network 192.168.1.0 route-map tagommunity
neighbor 10.10.1.10 remote-as 65002
neighbor 10.10.1.10 route-map prepend out
!
ip community-list 1 permit 65001:9999
!
route-map prepend permit 10
match community 1
set as-path prepend 65001 65001 65001
!
route-map prepend permit 20
!
route-map tagcommunity permit 10
set community 65001:9999
!

Regards


Le 2011-01-17 à 10:10, Elmar K. Bins a écrit :

> Re guys,
> 
> the prefixes I give out are being rooted by "network" entries with
> a route-map attached (like "network a.b.c.d/e route-map <rm>").
> 
> In that route-map, I'm simply prepending an ASN ("as-path prepend <as>").
> 
> Well - that prepend never makes it to the outside world. Source ASN is
> simply my ASN, the desired <as> is nowhere to be found.
> 
> Am I wrong in assuming it should work that way?
> 
> Oh, platform is an ASR1002, IOS-XE 12.2(33)XNC1t.
> 
> Didn't try my 7301s yet...
> 
> Elmar.
> 
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Harold Ritter
Directeur Technique/Technical Leader
Advanced Services Central Engineering
CCIE 4168 (R&S, SP)

harold at cisco.com
Téléphone: 514 847 6856

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