Inter-AS option C - DO and Do NOT -How to ?

Hi Folks,

I've been researching Option C inter-as connectivity for a while and I can
see lots of different configurations on the net that do not necessarily
correct.

*Appreciate that someone verify that my understanding is correct:*

Assume the following setup.

CE1-----PE1 ----P1 ------ ASBR1 -------ASBR2 -----------P2-----------PE2
-------------CE2

               <----------------------------------VPNv4 BGP
------------------------->

                                <--IPv4 eBGP+ label-->

PE loopback reachability will be achieved on one of the following ways:

*1- Internal Gateway Protocol (IGP) and Label Distribution Protocol
(LDP):*The ASBR can redistribute the IPv4 routes and MPLS labels it
learned from
EBGP into IGP and LDP and vice versa.

-Send-label only needs to be configured *only *on ASBR1 and ASBR2
-Nexthop-unchanged on PEs.
- PE2 Loopback advertised via IGP to ASBR2 then via ebgp to ASBR1 then
redistributed along with IPv4 label to IGP. PE1 will learn it via IGP.
- NO iBGP between PE and ASBRs.

How to verify label stack on P2 (is there any way to see the whole 3 labels
on P router ??)

*2-Internal Border Gateway Protocol (IBGP) IPv4 label distribution: *The
ASBR and PE router can use direct IBGP sessions to exchange VPNv4 and IPv4
routes and MPLS labels.

-Nexthop-unchanged on PEs.
- Extended iBGP between PE and ASBR. ASBR sends IPv4 information with
labels to PE.
- Neighbour x.x.x.x send-label on ebgp to ASBR *AND *on iBGP to PE.
-PE1 learns VPN label and IPv4 label PE2 via iBGP from ASBR1 and it uses
ASBR1 NH as the next hop to reach PE2 Loopback. (Is this sequence correct ?)
- when ASBR1 advertise PE2 LP to PE1 ,it uses* ASBR2 address *as the NH.
Therefore, PE1 needs to know about ASBR1-ASBR2 subnet.

Please verify if the following methods for distributing ASBR1 NH to PE1 is
correct.

- redistribute connected on ASBR1 with passive interface on the interface
toward ASBR2
- *Next-hop self *
- network x.x.x.x under BGP.

*Are all of above methods are correct ??? * (cisco guide used the first one.
http://www.cisco.com/en/US/docs/ios/12_2t/12_2t13/feature/guide/ftiasl13.html )

Thanks in advance

Jeremy

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Received on Mon May 21 2012 - 12:03:33 ART