Subject: [OSPF] Sham link query

From: "Lokesh Jain" <[email-masked]>
Date: Thu, 13 Mar 2008 14:42:41 +0530

Hi All,

I have a doubt regarding packet (data packets, lsa, hello packets)
forwarding on Sham Link.

On two different PEs, we establish a Sham link between two VRFs. The Sham
Link End point Address on each PE is associated with one OSPF instance and
advertised by the BGP into the backbone. Is this advertisement done in the
same way as for any other route (advertising a VPN label for the route) ?

So on both PEs, the routing entry (BGP) will be stored in corresponding
VRF(along with VPN label) along with next hop information (which will be
taken from default VRF).

On this sham link, hello/dd/LSA packets (basically OSPF originated packets)
as well as data packets (host originated) will be forwarded. What is the
difference in the labels applied by the ingress PE router for both type of
packets, if any?

-- 
~~~~~~~~~~~~~
Thanks & Regards,
~~~~~~~~~~~~~
Lokesh Jain
Senior Software Engineer,
Samsung India Software Operations Pvt. Ltd.,
Bagmane Tech Park, C V Raman Nagar,
Bangalore.
Mob: 9880611348
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You always miss 100% of the chances u don't take
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From: Peter Psenak <[email-masked]>
Date: Thu, 13 Mar 2008 15:17:40 +0100

Lokesh,

Lokesh Jain wrote:

> On two different PEs, we establish a Sham link between two VRFs. The 
> Sham Link End point Address on each PE is associated with one OSPF 
> instance and advertised by the BGP into the backbone. Is this 
> advertisement done in the same way as for any other route (advertising a 
> VPN label for the route) ?

SL endpoint addresses are addresses that reside in the VRF space and are 
advertised as BGP VPNv4 routes. SL endpoint addresses should not be 
advertised by OSPF itself.

> VRF(along with VPN label) along with next hop information (which will be 

right.

> 
> On this sham link, hello/dd/LSA packets (basically OSPF originated 
> packets) as well as data packets (host originated) will be forwarded. 
> What is the difference in the labels applied by the ingress PE router 
> for both type of packets, if any?

no difference if the 'host originated' above means originated by the PE 
and sent to the SL destination address on remote PE.

Peter

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