8 Replies Latest reply: Feb 28, 2017 11:01 AM by Elvin Arias RSS

    vrf-lite question


      Hi all,

      I have the following topology:



      I can't seem to form neighbourship between the 'common' router and 'voice' router.

      Here is my configurations:


      common router

      ip vrf VOICE



      interface GigabitEthernet0/1.2

      encapsulation dot1Q 2

      ip vrf forwarding VOICE

      ip address


      router ospf 1 vrf VOICE

      network area 0



      voice router

      interface GigabitEthernet0/1

      ip address

      duplex auto

      speed auto

      media-type rj45


      interface GigabitEthernet0/2

      ip address

      duplex auto

      speed auto

      media-type rj45


      router ospf 1

      network area 0


      Did a debug and both routers receive hello packets.

      Any help would be appreciated.



        • 1. Re: vrf-lite question

          Hi PKGranville


          Could you please post the output of a debug ip ospf adj



          • 2. Re: vrf-lite question

            never mind, your subnet mask is wrong


            ip address




            ip address

            These need to match for OSPF to form an adjacency


            • 3. Re: vrf-lite question
              Steven Williams

              Yes, Look up the requirements that each neighbor needs to meet to form an adjacency.

              • 4. Re: vrf-lite question

                Check the Subnet mask .

                • 5. Re: vrf-lite question

                  I tried this in GNS3 and noticed a couple of things.

                  1. The common router seemed to want to require a router-id for ospf. (don't think this is the issue though)
                  2. check the vlans.  Typically the port between the common router and the switch would be a trunk and the port from the switch to the voice should be on vlan 2.  At least that's my thoughts. 



                  I don't believe it to be the subnet mask so much because a /30 would fit .1 and .2 within it.


                  I'm going to lab this on my routers to see what I get.

                  • 6. Re: vrf-lite question

                    It is the subnet mask as others have stated above.  Here's my debug:


                    R2voice#debug ip ospf hello

                    OSPF hello debugging is on


                    Jan  2 13:05:50.311: OSPF-1 HELLO Fa0/0: Send hello to area 0 from

                    Jan  2 13:05:53.271: OSPF-1 HELLO Fa0/0: Rcv hello from area 0

                    Jan  2 13:05:53.271: OSPF-1 HELLO Fa0/0: Mismatched hello parameters from

                    Jan  2 13:05:53.271: OSPF-1 HELLO Fa0/0: Dead R 40 C 40, Hello R 10 C 10 Mask R C


                    I'm thinking that the R=Received and the C=connected(or configured locally) so the received mask is different than the connected/configured and so is causing a mismatched hello error.  It is not going to form an adjacency.





                    If you have the official cert guide on page 274 under ospf fundamentals

                    subnet mask must match.

                    • 7. Re: vrf-lite question

                      mismatch in subnet mask is the problem, HELLO packet that is used to form adjacency contains the below and they have to match


                      1. Router ID of the origination router
                      2. Area ID  of the originating router
                      3. IP address and subnet mask of the origination interface
                      4. Authentication type and its information of originating interface
                      5. HELLO interval of originating interface
                      6. Router Dead Interval of originating interface
                      7. Router Priority
                      8. DR and BDR
                      9. 5 flag bits about capability
                      10. Router IDs of originating router's neighbors
                      • 8. Re: vrf-lite question
                        Elvin Arias

                        First, verify connectivity between the devices inside the VRFs, e.g., "ping vrf <NAME> <DST IP ADDRESS>". After that, verify your OSPF in order to validate if everything is correct in order to form an adjacency.