Hi All,
1- my problem is to understand if a vrf can be used on a router to learn routes from a second vrf, and propagate them to a 3rd one. Here is an example:
PE1
ip vrf Cust-A
rd 100:1
route-target export 100:1
route-target import 100:1
ip vrf CoreVRF
rd 100:2
route-target export 100:2
route-target import 100:2
route-target import 100:1
ip vrf Cust-B
rd 100:3
route-target export 100:3
route-target import 100:3
route-target import 100:2
interface Loopback1
ip vrf forwarding Cust-A
ip address 1.1.1.1 255.255.255.255
interface Loopback2
ip vrf forwarding CoreVRF
ip address 2.2.2.2 255.255.255.255
interface Loopback3
ip vrf forwarding Cust-B
ip address 3.3.3.3 255.255.255.255
Now, let's start with the statements I believe to be correct:
sh ip route vrf Cust-A should show only 1.1.1.1/32 , right?
sh ip route vrf CoreVRF should show 1.1.1.1/32 (imported from Cust-A), and 2.2.2.2 right?
Now the tricky bit: what should I see on show ip route vrf Cust-B ?
3.3.3.3/32 (surely, as Cust-B vrf owns this route!)
2.2.2.2/32 (surely, as Cust-B vrf imports all routes from Core vrf)
1.1.1.1/32 ?? Some Cisco documentation says NO, because Core vrf has learned that route via leaking (from Cust-A vrf), therefore it will not leak it back out onto Cust-B vrf. But in my network, that is a mix of several Cisco routers on different IOS, I think I observed it happen at times, not in all instances. I am not toally sure, given the complexity of interleaking in my network, and that is why I am asking for help.
2- The second point is: would it make any difference if some of those routes were resident on a different PE (say PE2) and be learned by PE1 via MP-BGP ?
For example if this piece of config was removed from PE1, and added to PE2:
PE2
interface Loopback1
ip vrf forwarding Cust-A
ip address 1.1.1.1 255.255.255.255
Keeping all the remaining config on PE1 as above, would it make any difference to my question's answer?
3- And if this Lo1 network was on PE2 (like just shown in my point 2- ), but the import statement from Cust-A into Core vrf was set on PE2 only (and not on PE1), would I see all the 3 routes on PE1's show ip route vrf Cust-B?
Basically with these changes as compared to the config shown in point 1- :
PE1
no int lo1
ip vrf CoreVRF
rd 100:2
no route-target import 100:1
PE2
ip vrf Cust-A
rd 100:1
route-target export 100:1
route-target import 100:1
ip vrf CoreVRF
rd 100:2
route-target export 100:2
route-target import 100:2
route-target import 100:1
interface Loopback1
ip vrf forwarding Cust-A
ip address 1.1.1.1 255.255.255.255
4- And the last point, which is maybe the crucial one, is: is anyone aware of different default behavior set by Cisco from one router platform (and IOS) to another? I suspect that this "transit behavior" of a vrf is allowed by default on my 2901 -- 15.1(4)M2, while not allowed on my 7206 -- 12.4 (I can be more specific later on this IOS, if it's needed).
I am not in the position to replicate this in a lab, because its results may depend on the platforms used (and IOS), so whichever outcome I'd obtain wouldn't be 100% reliable.
Whoever can give some input, and also develop the topic further, would do me a big favor
Thanks in advance,
Luca
