OSPF Virtual-Link via unnumbered interface

Hello All!

I can't make work virtual link via unnumbered interface.

2 routers connect via serial p-t-p interface (both sides use unnumbered IP addreses). Routers formed ajacency successfuly.

But virtual links are down with cost 65535

 

Is it possible to configure virtual link via unnumbered interfaces?

Comments

  • Try using Tun interface instead of using virtual link.....


  • ok, tunnel works perfectly well but what about virtual link?

    Why virtual link doesnt come up? Are there any ways to come around this issue?

  • The virtual link can only be formed wid to ABRs and u have to spacify the destination of virtual link which cannot be unnemberd (in ur case) so it so not possible widout the destination of the virtual link....thats wt i think but do check it from experts as well.....

  • The virtual link can only be formed wid to ABRs and u have to spacify the destination of virtual link which cannot be unnemberd (in ur case) so it so not possible widout the destination of the virtual link....thats wt i think but do check it from experts as well.....

    the destination of virtual link isnt unnumbered interface of other router , it is other router's ID I my case it's different from (but can be set the same) unnembered IP...

  • An OSPF Virtual-Link always has a router-id as its destination - OSPF will figure out how to get there through the area specified. The virtual-link will need to reach its destination by traversing only through the specified ospf area.

    If your connecting interface is in the specified ospf area, the virtual-link should work.

    Try "show ip ospf interface brief" to verify which area your interfaces are in.

  • It should but it isnt...

     

    sh ip ospf interf brief shows what vl0 is down and has cost 65535 (I cant copy/paste real output at the moment).

    Yes I know Vlink doesnt come up if it has cost 65535 but why it has it???

    Serial connection has cost of 64...

     

  •  

     

    so I reproduced the topology and can show you outputs and configs:

     

     

    R4:

     

    Rack1R4#i
    Interface                  IP-Address      OK? Method Status                Protocol
    Serial0/1/1                150.1.4.4       YES TFTP   up                    up     
    Loopback0                  150.1.4.4       YES NVRAM  up                    up  

     Loopback100                100.100.100.100 YES manual up                    up  

    Rack1R4#beg router ospf
    router ospf 1
     router-id 4.4.4.4
     log-adjacency-changes
     area 4 virtual-link 5.5.5.5
     network 150.1.4.4 0.0.0.0 area 4

    network 100.100.100.100 0.0.0.0 area 0

    Rack1R4#sh ip ospf int brie
    Interface    PID   Area            IP Address/Mask    Cost  State Nbrs F/C
    Lo100        1     0               100.100.100.100/24 1     LOOP  0/0
    VL0          1     0               0.0.0.0/0          64    P2P   0/0
    Lo0          1     4               150.1.4.4/24       1     LOOP  0/0
    Se0/1/1      1     4               0.0.0.0/0          64    P2P   1/1

    Rack1R4#sh ip ospf nei

    Neighbor ID     Pri   State           Dead Time   Address         Interface
    5.5.5.5           0   FULL/  -        00:00:35    150.1.5.5       Serial0/1/1

     

    ==================================================================

    Rack1R5#i
    Interface                  IP-Address      OK? Method Status                Protocol
    FastEthernet0/0            163.1.5.5       YES NVRAM  up                    up     
    Serial0/1/1                150.1.5.5       YES TFTP   up                    up     
    Loopback0                  150.1.5.5       YES NVRAM  up                    up     

    Rack1R5#beg router ospf
    router ospf 1
     router-id 5.5.5.5
     log-adjacency-changes
     area 4 virtual-link 4.4.4.4
     network 150.1.5.5 0.0.0.0 area 4
     network 163.1.5.5 0.0.0.0 area 7

    Rack1R5#sh ip ospf interf brie
    Interface    PID   Area            IP Address/Mask    Cost  State Nbrs F/C
    VL0          1     0               0.0.0.0/0          64    P2P   0/0
    Lo0          1     4               150.1.5.5/24       1     LOOP  0/0
    Se0/1/1      1     4               0.0.0.0/0          64    P2P   1/1
    Fa0/0        1     7               163.1.5.5/24       1     DR    0/0

     

    Rack1R5#sh ip ospf nei

    Neighbor ID     Pri   State           Dead Time   Address         Interface
    4.4.4.4           0   FULL/  -        00:00:39    150.1.4.4       Serial0/1/1

    =================================================================================

     

    Vlink has cost of 64 but still down!!

     

    Any comments?

     

  • Hay Darrell i want to clear on more thing abt Virtual links and tun int in OSPF...if we are using virtual links nd that area is also genrating summary address so virtual links will leak to more specifice routes or not.2nd thing is if we are genrating summary address so its better to use tun int.Plz clear this too

  • when ur creating a virtual link using the unnumbered command the virtual link will not come up if the other end of the virtual link is reachable via the unnumbered interface because when the hellos for the virtual link are generated they will have a source ip of 0.0.0.0 (as unnumbered interface has no ip address and in the virtual link the ip address of the outgoing intreface is used)...

    so that is the reason they virtual link is not comming up ur case...

    another reason is that in virtual links the hellos packets are unicast not multicast, so as both the interface has no ip address of their own as they are unnumbered they will never be able to exchange hello's and thus no adj..

    HTH

    Peace

     

  • So, you mean NO SOLUTION ?

    Only tunnel?

  • yeah that is the only solution in mind, lets ask the experts if there is any work around with it..

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