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Inter-AS MPLS

  • From: "Andris Zarins" <andris.zarins@microlink.lv>
  • Date: Tue, 31 May 2005 17:20:02 +0300
  • Resent-Date: Tue, 31 May 2005 10:20:16 -0400
  • X-Scanned-By: MIMEDefang 2.45

Hi,

 

As I know – all next-hops (loopbacks) inside both AS must be distributed via BGP along with respective labels using ‘send-label’ keyword. This must be done to make sure there is end to end LSP between source and destination PE boxes (a label for each BGP next-hop).

 

Setup – inside one AS all iBGP sessions are created between respective loopbacks.

 

Question – if eBGP session between different AS is created NOT between loopbacks, but between IP addreses of one subnet (without ebgp-multihop), is this a mandatory that loopback addreses (used for intraAS peering) are advertised with send-label between AS? Please correct me if I’m wrong – there must be only a label for BGP next-hop, it doesn’t matter is it loopback or some physical interface. Right?

 

Same story using ‘show commands’

 

Using ‘show ip bgp vpnv4 vfr test labels x.x.x.x’ I can find out next hop for some prefix, right? Then using show ‘show mpls forwarding-table’ I can find out if there is a label for that BGP next hop. And if there is correct next-hop and there is a label for that next hop – everything should work, at least so far. Right?

 

 

Andris?