[j-nsp] as-path rewrite

[Peter Lundqvist]

Sorin CONSTANTINESCU wrote:
> On 9/27/05, Rafal Szarecki (WA/EPO) <rafal.szarecki at ericsson.com> wrote:
> 
>>Sorin,
>>
>>The juniper "set loops 2" is the same as ciscos "allow-in". So What do not use them if you use allows-in?
> 
> 
> I didn't find a per-neighbor setting of loops.
> 

lunkan at junos_access# set routing-options autonomous-system 1111 loops 2



> 
>>Try to use AS-overide on ebgp session. this has to be don on AS2 CE on session to global instance.


lunkan at junos_access# set routing-instances vrf_1 protocols bgp group x 
as-override



>>
>>"local-as" do not solve your problem. This do not overwrite real AS. thay just add "virtual" AS in between neighbors. If you define AS3 as local AS between AS 1 and AS 99, on path you will see "1 3 99 2".
>>
> 
> 
> I had a hunch...
> 
> 
>>Rewrittink of AS-PATH is impossible. And this is good. Let imagine World wide inconsistency. AS pre RFC1771 AS-PATH attribute is used to AVOID LOOPS. So any misteak here can ...
>>
> 
> 
> I can definatelly see the advantage of not rewriting the AS-PATH.


and the possability for doing mistakes :)

> 
> 
>>The other concept is to as customer to:
>>do not advertize prefixes lerned from VPN to Internet connection (wuith AS1 on path)
>>create aggregate route on CE in AS2 which represent whole AS1.
> 
> 
> AS1 has 2 transit providers (AS2 is one of them). If AS2 aggregates
> the prefix received from AS1, wouldn't there be a problem that the
> same prefix have origin in AS1 and AS2?
> 
> 
> 
> The ugly solution that the customer agreed to configure on his routers
> was an EBGP Multihop session between 2 routers in AS1/AS2.
> 
> 
>>Sorin, are you work for ROMTELECOM?
> 
> 
> No. Why do you ask?
> 
> 
> 
> PS: Brick asks you if you threw his jacket :)
> 
> 
>>Rafal Jan Szarecki JNCIE #136
>>Senior Consultant - Datacom Networks
>>Ericsson Poland EPO/S/D
>>Office: +48 22 6916635
>>ECN:    837 6635
>>Mobile: +48 602418971
>>Skype: callto://Rafal_Szarecki <callto://Rafal_Szarecki/>
>>
>>
>>
>>
>>>-----Original Message-----
>>>From: juniper-nsp-bounces at puck.nether.net
>>>[mailto:juniper-nsp-bounces at puck.nether.net]On Behalf Of
>>>Sorin CONSTANTINESCU
>>>Sent: Tuesday, September 27, 2005 12:17 PM
>>>To: juniper-nsp at puck.nether.net
>>>Subject: [j-nsp] as-path rewrite
>>>
>>>
>>>Hi, all.
>>>
>>>I have the following topology:
>>>
>>>AS1 - AS99 (L3 Mpls VPN) - AS2 - AS99 - INTERNET
>>>
>>>My customer (AS2 - public AS Number) buys from the company i work for
>>>2 services:
>>>
>>>1) Internet Access
>>>2) VPN between his location, and AS1 (also public AS Number).
>>>
>>>The problem i have is that when i receive a prefix originated by AS1
>>>on the Internet Transit BGP session, the AS-PATH is: 1 99 2 . Our
>>>network is a mixture of Juniper and Cisco routers. I used "allowas-in"
>>>on the neighbor to the customer, but the Juniper routers won't import
>>>this prefix throughout the network. I know i can use
>>>
>>>a at R1# set loops ?
>>>Possible completions:
>>>  <loops>              Maximum number of times this AS can be in an AS
>>>path (1..10)
>>>[edit routing-options autonomous-system]
>>>a at R1# set loops
>>>
>>>... but i don't consider this an option.
>>>
>>>Has anyone ever ran into this problem? As far as i see it, i have the
>>>following options:
>>>
>>>- use private "local-as" for the BGP sessions between AS99 and AS1/AS2
>>>for the MPLS VPN BGP sessions (haven't tested this one so far)
>>>- ask the customer to configure EBGP Multihop between AS1 and AS2, so
>>>that my own AS won't be in the AS-PATH
>>>
>>>I wish i could AS-PATH rewrite :))
>>>
>>>Thanks,
>>>--
>>>Sorin CONSTANTINESCU
>>>Cisco CCNP / JNCIA #845
>>>consta at gmail.com
>>>
>>>_______________________________________________
>>>juniper-nsp mailing list juniper-nsp at puck.nether.net
>>>http://puck.nether.net/mailman/listinfo/juniper-nsp
>>>
>>
> 
> 
> --
> Sorin CONSTANTINESCU
> Cisco CCNP / JNCIA #845
> consta at gmail.com
> 
> _______________________________________________
> juniper-nsp mailing list juniper-nsp at puck.nether.net
> http://puck.nether.net/mailman/listinfo/juniper-nsp


-- 
Peter Lundqvist - Beta Engineering
Juniper Networks
Mobile: +46702060472
URL   : http://www.juniper.net