[c-nsp] Down-bit or external route tag cleared by capability vrf-lite ?

[Vitkovsky, Adam]

Interesting question 
If CE1 advertises a prefix to mpls via PE1
Than on PE2 during redistribution of mp-bgp to ospf in vrf context the down bit is set in the header of LSA3 and external route tag on LSA5 encoded as the mp-bgp as# by default or according to the cmd: "domain-tag <tag>"

Now ospf process on PE2 advertises the prefix to CE2
Since ospf process on CE2 is configured with "capability vrf lite" -the PE checks are suppressed on CE2 meaning:
LSA3 -even though it has a down bit set -it is assigned a routing bit 
     Thus considered for routing and redistributed into MP-BGP on CE2
LSA5 -if the MP-BGP as# on the CE2 is different from that used in mpls
     The LSA would get the routing bit and redistributed into MP-BGP on CE2
     -if the MP-BGP as# on the CE2 is the same as the one in mpls
      Or if the external route tag is set manually on the CE2 to match with
      The one set in mpls (using cmd: "domain-tag")
     Than the "capability vrf lite" kicks in setting the routing bit on this 
     LSA anyway and the LSA would be redistributed to MP-BGP on CE2

Now what happens when the MP-BGP on CE2 redistributes this prefix back to ospf in another vrf 
For LSA3 -nothing changes either the down bit is kept or set again
For LSA5 -I'm not sure whether the external route tag is kept 
	    or rewritten to value to match up with the MP-BGP AS# on CE2 


adam
 
-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of selamat pagi
Sent: Monday, November 14, 2011 1:41 PM
To: cisco-nsp
Subject: [c-nsp] Down-bit or external route tag cleared by capability vrf-lite ?

Just want to confirm my unterstanding
(and don't have currently lab access to verify)

SETUP:

CE1 --- OSPF --- PE1
|                           |
OSPF                MP-BGP
|                            |
CE2 --- OSPF --- PE2

*CE2 is vrf-lite enabled*

*
*
Does CE2 just ignore the Downbit or th Domain-tag  OR does it actually
clear it ?

My unterstanding is, that CE2 just ignores it. Is this correct ?

cheers, keti
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