[j-nsp] as-path rewrite

[Sorin CONSTANTINESCU]

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.

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

> 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