Subject: Ospf sham link in layer3 vpns

From: "Banerjee, Gargi" <[email-masked]>
Date: Mon, 3 Feb 2003 17:30:41 -0500

Hi all:

I had a question on creating ospf adjacency between PE routers over a sham
link.
In draft-rosen-vpns-ospf-bgp-mpls-05.txt, sham links are introduced to
overcome the problem due to backdoor connectivity.
The draft says that sham links can be created manually or by automatic
configuration.

Once created they are advertised by a PE in a type 1 lsa into the area.
But, since the sham link is virtual, this type 1 lsa must actually be
carried in a MP-iBGP update to reach the other PE- is this understanding
correct ?

Thanks
Gargi

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From: Acee Lindem <[email-masked]>
Date: Mon, 3 Feb 2003 18:21:57 -0500

> carried in a MP-iBGP update to reach the other PE- is this understanding

No. Once the sham link is up (internal signaling is
implementation specific and unspecified), you can send any type
packet between PE routers. The sham link traffic between the
PE routers will be carried over the MPLS LSP (or other tunnel)
in the provider's network.

Note that draft-rosen-vpns-ospf-bgp-mpls-05.txt is under the auspices
of the PPVPN WG.

--
Acee

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From: Peter Psenak <[email-masked]>
Date: Tue, 4 Feb 2003 09:09:58 +0100

Gargi,

> carried in a MP-iBGP update to reach the other PE- is this understanding

two endpoints of the sham-link establish OSPF adjacency over the VPN backbone and LSAs are flooded
over this adjacency.

Peter