I stand corrected. I just tried this out and by default, when I
redistributed OSPF into MP-BGP, it automatically added a domain-id
type of 0x0005 and a value which is somehow related to the process ID
for OSPF. With both process ID's being 2 (router ospf 2 vrf VPNA), I
get the following output:
R5(config-subif)#do sh ip bgp vpn all 200.0.0.1
BGP routing table entry for 256:1:200.0.0.1/32, version 25
Paths: (1 available, best #1, table VPNA)
Advertised to update-groups:
1
Local
150.50.15.1 from 0.0.0.0 (200.0.0.5)
Origin incomplete, metric 2, localpref 100, weight 32768, valid,
sourced, best
Extended Community: RT:256:1 OSPF DOMAIN
ID:0x0005:0x000000020200 <<<-------
OSPF RT:0.0.0.0:2:0 OSPF ROUTER ID:150.50.15.5:512,
mpls labels in/out 24/nolabel
R5(config-subif)#do sh ip bgp vpn all 200.0.0.4
BGP routing table entry for 256:1:200.0.0.4/32, version 34
Paths: (1 available, best #1, table VPNA)
Flag: 0xA20
Not advertised to any peer
Local
200.0.0.2 (metric 65) from 200.0.0.2 (200.0.0.2)
Origin incomplete, metric 65, localpref 100, valid, internal, best
Extended Community: RT:256:1 OSPF DOMAIN
ID:0x0005:0x000000020200 <<<-------
OSPF RT:0.0.0.0:2:0 OSPF ROUTER ID:150.50.24.2:512,
mpls labels in/out nolabel/21
The CE routers route tables shows each route as an internal OSPF route.
But if I change one of the routers so that the process ID is now 3, I
get the following output:
R5(config-subif)#do sh ip bgp vpn all 200.0.0.4
BGP routing table entry for 256:1:200.0.0.4/32, version 33
Paths: (1 available, best #1, table VPNA)
Flag: 0x820
Not advertised to any peer
Local
200.0.0.2 (metric 65) from 200.0.0.2 (200.0.0.2)
Origin incomplete, metric 65, localpref 100, valid, internal, best
Extended Community: RT:256:1 OSPF DOMAIN
ID:0x0005:0x000000030200 <<<-------
OSPF RT:0.0.0.0:2:0 OSPF ROUTER ID:150.50.24.2:512,
mpls labels in/out nolabel/21
The route table on the CE router shows this route as an external route.
>From the router where I have OSPF process ID 3, I can then enter the command:
router ospf 3
domain-id type 0005 value 000000030200
This will re-write the domain ID value making it the same on both ends
and the CE route table again shows the route as an internal OSPF
route.
BTW, configuring a domain-id on a non-PE router has no apparent effect.
On Sun, Aug 23, 2009 at 12:04 PM, jmangawang<[email protected]> wrote:
> For Item 2, I believe the domain-id option is used to preserve OSPF
> LSA types for prefixes as they are carried over an MP-BGP network. As
> far as I understand it, it's used on PE routers facing CE routers
> running OSPF. When you redistribute the vrf VPN into MP-BGP, it adds
> some extra info in the form of an extended community so that when it
> gets to the other side, the remote CE OSPF router will see those
> prefixes as O, IA, or external routes. Normally, you'd just get all
> external routes because of the redistribution into/from BGP.
>
> Anybody, please correct me if I'm wrong about the domain-id thing.
>
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