09-10-2009 05:13 AM
Hi All,
I have the following simple lab topology-
CE1-PE1-P2-PE3-CE2 while there is a backdoor link between CE1 and CE2.I have changed the bandwidth of this link to 1kbps so that it is least preferable.
The relevant configuration on PE1 router is-
interface Loopback 12
ip vrf forwarding CUST1
ip add 1.1.1.1 255.255.255.255
!
router bgp 100
..
address-family ipv4 vrf CUST1
network 1.1.1.1 mask 255.255.255.255
..
!
router ospf 1 vrf CUST1
area 0 sham-link 1.1.1.1 2.2.2.2 cost 2
!
The similar configuration on PE3 router too.
The "show ip ospf sham-link" output shows following-
PE1#sh ip ospf sham
Sham Link OSPF_SL0 to address 2.2.2.2 is up
Area 0 source address 1.1.1.1
Run as demand circuit
DoNotAge LSA allowed. Cost of using 2 State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40, Wait 40,
Hello due in 00:00:08
There is no adjacency formed. I also cannot ping 2.2.2.2 from PE1 router.
I am using 2691 with 12.4(25a) IOS.
Please share your thoughts.
Amit.
Solved! Go to Solution.
09-11-2009 06:51 AM
Amit,
> LDP was properly configured becoz the "show ip bgp vpnv4 all" command showed proper output including the prefixes 1.1.1.1/32 and 2.2.2.2/32 on both PE routers.
This command doesn't tell you anything about the LDP signaled LSP.
Can you do a "show ip cef vrf CUST1 2.2.2.2" from PE1. You should see a 2 labels for that prefix (1 IGP label and 1 service label) if the two PEs are not directly connected. Make sure that the LSP is not broken along the way as well.
Regards
09-10-2009 05:55 AM
Hi Amit
If possible could you post all the configs. There might be problem with with state.
regards
shivlu jain
09-10-2009 10:11 AM
Amit,
Make sure LDP is properly configured between PE1 and PE3 and that it is up and running. This could certainly cause the adjacency not coming up on the sham-link and the pinging not to work.
Regards
09-10-2009 06:23 PM
Hi Guys,
LDP was properly configured becoz the "show ip bgp vpnv4 all" command showed proper output including the prefixes 1.1.1.1/32 and 2.2.2.2/32 on both PE routers.
Here's complete config on PE1 router-
mpls label protocol ldp
mpls ldp router-id Loopback 0 force
!
ip vrf CUST1
rd 1:1
route-target both 1:1
!
interface Loopback 0
ip address 10.200.254.1 255.255.255.255
!
interface Loopback 12
ip vrf forwarding CUST1
ip address 1.1.1.1 255.255.255.255
!
interface serial 0/0
ip vrf forwarding CUST1
ip address 192.168.1.1 255.255.255.252
!
interface fastethernet 0/0
description Link_to_P2
ip address 10.1.1.1 255.255.255.252
mpls ip
!
router ospf 100
network 10.1.1.0 0.0.0.3 area 0
network 10.200.254.1 0.0.0.0 area 0
!
router ospf 1 vrf CUST1
network 192.168.1.0 0.0.0.3 area 0
redistribute bgp 100 subnets metric 10
area 0 sham-link 1.1.1.1 2.2.2.2 cost 2
!
router bgp 100
neighbor 10.200.254.3 remote-as 100
neighbor 10.200.254.3 update-source Loopback 0
!
address-family vpnv4
neighbor 10.200.254.3 activate
neighbor 10.200.254.3 send-community both
exit-address-family
!
address-family ipv4 vrf CUST1
network 1.1.1.1 mask 255.255.255.255
redistribute ospf 1 vrf CUST1 metric 10 match internal external
exit-address-family
!
Both CE1 and CE2 routers also had prefixes 1.1.1.1/32 and 2.2.2.2/32 in their routing tables advertised by PE1 and PE3 resp.
I can't understand why PE1 or PE3 router could not ping 2.2.2.2 or 1.1.1.1 resp. thru the backdoor link.
09-11-2009 06:51 AM
Amit,
> LDP was properly configured becoz the "show ip bgp vpnv4 all" command showed proper output including the prefixes 1.1.1.1/32 and 2.2.2.2/32 on both PE routers.
This command doesn't tell you anything about the LDP signaled LSP.
Can you do a "show ip cef vrf CUST1 2.2.2.2" from PE1. You should see a 2 labels for that prefix (1 IGP label and 1 service label) if the two PEs are not directly connected. Make sure that the LSP is not broken along the way as well.
Regards
09-11-2009 04:22 PM
Spot-on Harold. Somehow missed to advertise the Loopback 0 address of P2 which I was using as LDP router-id. I thought I saw 2 labels for the prefixes and took it for granted that LDP neighborship was formed between peers.
Anyway, it is working as it should.
Thanks mate.
09-11-2009 05:22 PM
I would just like to add a point that the VPN-label for 2.2.2.2 will never be used unless the router-id is set to 2.2.2.2 on PE3 router.
Thanks again.
Amit.
09-12-2009 08:22 AM
Amit,
There is no such restriction. You tunnel endpoint end your RID can be different.
Regards
09-12-2009 12:52 PM
Sorry, I meant your sham-link end point and your RID can be different.
Regards
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