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

[Harold Ritter]

Hi Elmar,

See comments in-line.

Le 2011-01-17 à 17:13, Elmar K. Bins a écrit :

> Re Harold,
> 
> hritter at cisco.com (Harold Ritter) wrote:
> 
>> 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).
> 
> Thanks for looking this up. I would not mind the AS sticking there, though,
> since this is just like "faking the origin" for a customer, and I would
> gladly have this in the iBGP, too.


This is not an option since it goes against the RFC and the iBGP peer receiving such an update would in the best case reject the update and in the worst case would have an unpredictable behavior.

> 
>> 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:
> 
> I know, but it's a lot more clumsy, since I need to
> 
>  - include route-maps on every peer/transit
>  - must remember to put all of those prepend-communities into every route-map
> 
> Clumsy, clumsy, clumsy. I hate it already.
> 
> Nonetheless, if the feature's not there, it can't be helped...
> 
> Thank you guys (and I was sure I've seen it work!)
> 							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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