Hello Claudio,
I'm using AS 65426.
This is the UPDATE message my bgpd sends to my neighbor :
Update Message (2), length: 54
Origin (1), length: 1, Flags [T]: IGP
0x0000: 00
AS Path (2), length: 4, Flags [T]: 23456
0x0000: 0201 5ba0
Next Hop (3), length: 4, Flags [T]: 192.168.53.113
0x0000: c0a8 3571
AS4 Path (17), length: 6, Flags [OT]: <4 bytes AS>
0x0000: 0201 0003 039c
Updated routes:
46.226.x.x/21
Regards,
Cédric
Le 29/07/2013 23:37, Claudio Jeker a écrit :
> On Mon, Jul 29, 2013 at 09:33:55AM +0200, OCEANET - Cédric BASSAGET wrote:
>> Hello,
>>
>> I'm trying to replace two cisco routers by two openBGPd routers.
>> A have 3 neighbors, two with 4-bytes AS, and one which only supports
>> 2-bytes AS for now.
>> I have a 4-bytes AS too.
>>
>> So in my bgpd.conf, I have :
>>
>> ...
>> AS <my 4bytes> <a 2bytes AS>
>> network z.z.z.z/21
>> ...
>> neighbor <neighbor's ip address> #a neighbor which supports 4 bytes AS
>> {
>> remote-as <neighbor's AS>
>> set prepend-self 1
>> }
>> ...
>> neighbor <neighbor's ip address> #a neighbor which supports 2 bytes
>> AS only
>> {
>> remote-as <neighbor's AS>
>> set prepend-self 2
>> }
>> ...
>>
>> My problem is that my second neighbor return this message :
>>
>> neighbor : received notification: error in UPDATE message, AS-Path
>> unacceptable
>>
>> I think bgpd is trying to prepend the neighbor which does not support
>> 4bytes AS with... a 4 bytes AS, due to the "set prepend-self 2".
>>
>> Now, time for the questions :
>> - Is it openBGPd's normal behavior ?
>> - Is there a way to force prepending with the 2 bytes AS ? I saw
>> "announce as-4byte (yes|no)" in manpage, is this option designed for that ?
>>
> OpenBGPD will prepend with AS_TRANS (23456) if the system has a 4-byte AS.
> This comes from the fact that internally all AS_PATHes are 4-byte and we
> "deflate" the AS_PATH for those session that can only handle the 2-byte
> ones. Doing that causes all 4-byte AS nummbers to be replaced with
> AS_TRANS.
>
> What 2-byte AS are you using for the old connection? By default AS_TRANS
> would be used and then enforce neighbor-as would not trigger.
>
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