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

[David Rothera]

In all the training and documentation I have done you are always told to use the neighbour x.x.x.x route-map xxxx out method when you are changing/modifying attributes.

On 17 Jan 2011, at 16:59, Ramcharan, Vijay A wrote:

> I've never used that method to do as-prepending but I tried it in a lab
> and it didn't work. Perhaps I'm missing something as well. 
> 
> Reading the BGP-4 handbook by Parkhurst, page 250 says that "In theory,
> these commands allow you to modify a network's BGP attributes. In our
> experience, they are too buggy and should not be used."
> 
> I used the same route-map in a neighbor statement and it as-prepended as
> expected. 
> 
> router bgp 2
> bgp log-neighbor-changes
> neighbor 10.0.50.4 remote-as 4
> neighbor 10.0.50.5 remote-as 5
> !
> address-family ipv4
>  neighbor 10.0.50.4 activate
>  neighbor 10.0.50.4 route-map asprepend out	===> WORKS
>  neighbor 10.0.50.5 activate
>  no auto-summary
>  no synchronization
>  network 1.1.1.0 mask 255.255.255.0 route-map asprepend ===> Doesn't do
> anything 
> exit-address-family
> !
> route-map asprepend permit 10
> set as-path prepend 2 2 2
> !
> 
> Downstream-2600-4#show ip bgp 
> BGP table version is 19, local router ID is 10.0.50.4
> Status codes: s suppressed, d damped, h history, * valid, > best, i -
> internal,
>              r RIB-failure, S Stale
> Origin codes: i - IGP, e - EGP, ? - incomplete
> 
>   Network          Next Hop            Metric LocPrf Weight Path
> *  1.1.1.0/24       10.0.50.2                0             0 2 2 2 2 i
> *>                  10.0.0.5                               0 1 5 2 i
> Downstream-2600-4#
> 
> Vijay Ramcharan 
> 
> 
>> -----Original Message-----
>> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
>> bounces at puck.nether.net] On Behalf Of Elmar K. Bins
>> Sent: Monday, January 17, 2011 10:11 AM
>> To: cisco-nsp at puck.nether.net
>> Subject: [c-nsp] Preloading AS to static network entry via route-map:
> Duh?
>> 
>> 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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