6 Replies Latest reply: Oct 2, 2018 3:25 PM by jh RSS

    OSPFv3 area mismatch

    Richard

      Hi,

       

      I'm creating a very simple topology - see picture.

       

      The entire network is IPv6 and I'm running OSPFv3. R1 is Area 0, R3 is area 34. R4 is the ASBR between the two AS's.

       

      before configuring OSPFv3 all standard connectivity tests are fine. I enable OSPFv3 in area 0, all fine, neighbours come up. However as soon as I enable Area34, the console is awash with area mismatch errors.

       

      The mismatch errors occur as soon as OSPFv3 is enabled on R3 and the interface added to the area. This is prior to configuring Area34 on the Fa0/0 interface on R4.

       

      I can't understand why this is happening unless the Ether-switch is actually acting like a hub and broadcasting the LSA's to all the other devices?OSPFv3.PNG

       

      I feel like I'm missing something obvious but can't figure it out at all. I've dismantled and rebuilt this lab many times now with the same result - I've also tried swapping the etherswitch for a CumulusVx switch and the basic GNS3 Ethernet switch with the same result

       

       

      Configs are:

       

      R1

      Current configuration : 151 bytes

      !

      interface FastEthernet0/0

      no ip address

      speed auto

      duplex auto

      ipv6 address FE80::1 link-local

      ipv6 address 2014::1/64

      ipv6 ospf 1 area 0

       

      OSPF

      ipv6 router ospf 1

      router-id 1.1.1.1

       

      R3

      interface FastEthernet0/0

      no ip address

      speed auto

      duplex auto

      ipv6 address FE80::3 link-local

      ipv6 address 2034::3/64

      ipv6 ospf 1 area 34

       

      OSPF

      ipv6 router ospf 1

      router-id 3.3.3.3

       

      R4

       

      interface FastEthernet0/0

      no ip address

      speed auto

      duplex auto

      ipv6 address FE81::4 link-local

      ipv6 address 2034::1/64

      ipv6 ospf 1 area 34

      end

      !

      !

      interface FastEthernet0/1

      no ip address

      speed auto

      duplex auto

      ipv6 address FE80::4 link-local

      ipv6 address 2014::4/64

      ipv6 ospf 1 area 0

      end

      !

      !

      ipv6 router ospf 1

      router-id 4.4.4.4

        • 1. Re: OSPFv3 area mismatch
          Ing_Percy

          Hi!

           

          You must consider the following

          ospfv3.jpg

          The first place you must consider it the formation of adjacencies and an important requirement is the both neighbors is in the same area.

           

          The "key" is the configuration of ESW1, put its configuration

           

          If you want the ESW1 act as a L2 Switch, then it is the broadcast network OSPF and you must define a unique area with a unique subnet (in case of the switch is operating with default configuration-all interfaces in vlan 1) or define vlans to separate the traffic between area 0 and area 34

           

          Best regards!

          • 2. Re: OSPFv3 area mismatch
            Richard

            Thanks Ing_Percy,

             

            I understand the concept if it were a layer 3 switch with SVi's etc, but in this instance I have it in it's most basic configuration i.e. layer2.

             

            Additionaly the devices in Area0 are in a completely different subnet to the devices in Area34 - They have to be as two interfaces can't be in the same subnet on a router as I understand it.

             

            For clarity R1-R4 are in 2014::X/64 range and  R4 - R3 are in 2034::X/64 so they're in different subnets.

             

            This is why I'm confused as they're in completely different broadcast domains, the OSPF LSA's in area 0 shouldn't be getting to either R4 Fa0/0 or R4 Fa0/0, the only way I thought that could happen is if the switch were actually a hub and dumping the frames out of every port.

            • 3. Re: OSPFv3 area mismatch
              Ing_Percy

              Hi!

               

              If you are using default configuration in your ESW1, then all interfaces is in vlan 1 (same broadcast domain), then your hello packets arrives in another area (remember that L2 switch only see mac-address and not ip address), then the hello packets (multicast) can flooding all switchports and produces logs of mismatched area.

               

              Best regards!

              • 4. Re: OSPFv3 area mismatch
                Richard

                Thanks Ing_Percy,

                 

                I realised that as soon as I hit post :facepalm:

                 

                Appreciate the response, need to try being less stupid in the future!

                • 5. Re: OSPFv3 area mismatch
                  Ing_Percy

                  Hi!

                   

                  Not problem, All people in Cisco Learning Network grow with the discussions and publications, also I get better, so, don't worry.


                  Best regards!

                  • 6. Re: OSPFv3 area mismatch
                    jh

                    You could also create an ACL to deny the undesired OSPF traffic.