05-27-2008 06:37 AM - edited 03-05-2019 11:14 PM
In the document "OSPF Support for Multi-VRF on CE Routers". The new command "capability vrf-lite" should allow to split the router into multiple virtual routers, where each router contains its own set of interfaces, routing table, and forwarding table.
In my setup, I want to have 2 VRFs, sharing a common subnet with OSPF configured on this subnet. However, in this setup, the OSPF process hangs in the EXSTART state. After a while, the adjacency returns to the INIT phase, due to too many retransmissions.
What could be the problem ? Is it a valid configuration ? if not, what is the reason for not working ?
Here is the router configuration :
ip cef
!
ip vrf RT3
rd 7500:3
route-target export 7500:3
route-target import 7500:3
!
ip vrf RT4
rd 7500:4
route-target export 7500:4
route-target import 7500:3
!
interface Loopback3
ip vrf forwarding RT3
ip address 3.3.3.3 255.255.255.255
!
interface Loopback4
ip vrf forwarding RT4
ip address 4.4.4.4 255.255.255.255
!
interface FastEthernet0/0
description *** RT3 VRF Interface ***
ip vrf forwarding RT3
ip address 192.168.1.3 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
description *** RT4 VRF Interface ***
ip vrf forwarding RT4
ip address 192.168.1.4 255.255.255.0
duplex auto
speed auto
!
router ospf 3 vrf RT3
log-adjacency-changes
capability vrf-lite
redistribute connected subnets
network 192.168.1.3 0.0.0.0 area 0
!
router ospf 4 vrf RT4
log-adjacency-changes
capability vrf-lite
redistribute connected subnets
network 192.168.1.4 0.0.0.0 area 0
!
Here is the OSPF neighbor command output :
RT3-RT4#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
3.3.3.3 1 EXSTART/BDR 00:00:35 192.168.1.3 FastEthernet0/1
4.4.4.4 1 EXSTART/DR 00:00:31 192.168.1.4 FastEthernet0/0
Thank you for any help
Yves Haemmerli
05-27-2008 07:01 AM
Hi Yves,
!
!
ip vrf RT4
rd 7500:4
route-target export 7500:4
route-target import 7500:3
Did you intend to use 7500:4?
!
I'm not 100% sure that you are trying to learn routes between 2 vrfs,are you?
I don't think that 2 interfaces/vrfs can form adjacency.
HTH
Thot
05-27-2008 07:34 AM
Hi Thot,
Yes, it is exactly what I want to do : establish an OSPF adjacency between to Interfaces belonging to the same router but to different VRFs. If is not supported, do you know why ? I tested with RIP and it works perfectly
Thank you
Yves
NB : Your right, there is a typo in the configuration (import statement). Here is an updated version :
ip cef
!
ip vrf RT3
rd 7500:3
route-target export 7500:3
route-target import 7500:3
!
ip vrf RT4
rd 7500:4
route-target export 7500:4
route-target import 7500:4
!
interface Loopback3
ip vrf forwarding RT3
ip address 3.3.3.3 255.255.255.255
!
interface Loopback4
ip vrf forwarding RT4
ip address 4.4.4.4 255.255.255.255
!
interface FastEthernet0/0
description *** RT3 VRF Interface ***
ip vrf forwarding RT3
ip address 192.168.1.3 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
description *** RT4 VRF Interface ***
ip vrf forwarding RT4
ip address 192.168.1.4 255.255.255.0
duplex auto
speed auto
!
router ospf 3 vrf RT3
log-adjacency-changes
capability vrf-lite
redistribute connected subnets
network 192.168.1.3 0.0.0.0 area 0
!
router ospf 4 vrf RT4
log-adjacency-changes
capability vrf-lite
redistribute connected subnets
network 192.168.1.4 0.0.0.0 area 0
!
05-27-2008 09:17 AM
yves,
I'd apologize you. I missed understanding VRF-Lite on some points.OSPF can from adjacency between VRFs. I tested your lab. Ahh,It worked like a charm. My IOS is 12.4(7h). I'm not sure that this is an IOS problem. I'm waiting for my idol,HAROLD RITTER to shed some light on this. ;-)
Cheers,
Thot
05-27-2008 10:43 AM
Thot,
Thanks for raising the issue. I found the bugid that causes the issue I mentioned in my previous post.
BugID: CSCdu28706
Description:
ARP rejects requests from interfaces in different vrfs
This bug is fixed in 12.4(1), which explains why you are not seeing the same issue with 12.4(7).
Regards,
05-27-2008 10:18 AM
Yves,
I have seen this issue with certain IOS versions in the past. The issue is most probably that the dynamic ARP doesn't behave properly in the VRF context, which would explained why the ospf adjacency gets stuck in EXSTART, as the DB description messages are exchanged using unicast addresses. This would also explain why it worked with RIP, as it propagates updates using either the broadcast address (RIP) or the multicast address (RIPv2).
A workaround would be to configured static ARP entries in each VRF as follow:
arp vrf RT3 192.168.1.4
arp vrf RT4 192.168.1.3
Regards,
05-27-2008 10:42 AM
Harold,
Nice explanation! as always.
Thanks
Thot
05-27-2008 10:43 AM
Thanks Thot. It is always a pleasure.
05-27-2008 12:18 PM
Hi Thot and Harold,
Your are both really great ! Within a few hours, from the other side of the planet, you explained and solved my problem ! I tested the static ARP entries method and it works fine now. I really want to thank you for your valuable contribution.
My test lab was on a 2651XM platform, but the real customer environment will be on a Catalyst 6500 running native IOS version 12.2.(33)SXF. I will see if the bug is fixed or not ;-)
Thanks again a lot !
Yves
05-27-2008 01:07 PM
Yves,
You are very welcome.
I am not sure if you meant 12.2(18)SXF or 12.2(33)SXH. The issue is definitely fixed in both versions anyway.
Regards,
02-19-2019 07:28 PM
I know this is a old thread, I faced same problem when implement some work.
I place two ASA 5550s inside outside interface between two same nexus 9300 ileaf switches , and asa run in transparent mode.
I have many vrfs running on nexus 9300(because this is vxlan enviriment). I want to implement vrf ospf neighbor across transparent vlan on asa, there will be 200 vrf ospf neighbors across asa between same nexus 9300 on different vrf
does I need create loopback interface for each vrf on nexus 93 for ospf router id?
thank you
Jeremy
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