So is my problem a configuration issue, a problem in openbgpd or just
something that is undoable ?
Regards,
Cédric
Le 30/07/2013 09:01, OCEANET - Cédric BASSAGET a écrit :
> 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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OCEANET
---------------------------------------------------------------
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72190 SARGE LES LE MANS
[t] +33 (0)2.43.50.26.50
[f] +33 (0)2.43.72.21.14
[AGENCE D'ANGERS]
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49066 ANGERS
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http://www.oceanet.com
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