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setup ospf over frame relay in packet tracer

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  • setup ospf over frame relay in packet tracer

    hi everybody,

    I'm trying to setup ospf over frame realy in packet tracer.
    I was able to do it only with point to point subinterfaces.

    first, i found no "ospf neighbor" command so I cant setup neighbors manually in the hub (It's hub and spoke topology).

    when I'm trying to setup ospf with multipoint subinterfaces I can't make it work.
    I found only "ip ospf network broacast" and "ip ospf network point-to-point"
    commands and no "ip ospf network point-to-multipoint".

    i'll appreciate any help..

    thank you

  • #2
    Re: setup ospf over frame relay in packet tracer

    The neighbor command is missing for pedagogical reasons, --because you don't need it. Apparently frame-relay inverse-arp is also turned off.

    OSPF tricks itself into thinking its on broadcast media (ethernet) with a Hello time of 10-seconds instead of the 30-seconds it normally uses for non-broadcast media (serial). The easiest way to fix this is to put ip ospf network broadcast on each of the interfaces connected to the frame relay switch.

    interface Serial0/0/0
    ip address
    no ip split-horizon
    encapsulation frame-relay
    ! no frame-relay inverse-arp
    frame-relay map ip 130 broadcast
    frame-relay map ip 120 broadcast
    ip ospf network broadcast

    is the same as configuring
    ip ospf hello-interval 10
    ip ospf dead-interval 40

    R3#show ip ospf int ser0/0/0.31
    Serial0/0/0.31 is up, line protocol is up
    Internet address is, Area 0
    Process ID 1, Router ID, Network Type BROADCAST, Cost: 64
    Transmit Delay is 1 sec, State DROTHER, Priority 0
    Designated Router (ID), Interface address
    No backup designated router on this network
    Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    Neighbor Count is 2, Adjacent neighbor count is 1
    Adjacent with neighbor (Designated Router)

    As soon as the hello and dead intervals match, your interfaces will automagically become neighbors.

    R1#show ip ospf neighbor
    Neighbor ID Pri State Dead Time Address Interface 1 FULL/BDR 00:00:32 Serial0/0/0 0 FULL/DROTHER 00:00:32 Serial0/0/0

    R2#show ip route
    Codes: O - OSPF, IA - OSPF inter area is subnetted, 1 subnets
    O IA [110/65] via, 00:33:16, Serial0/0.123 is subnetted, 1 subnets
    O IA [110/65] via, 00:33:16, Serial0/0.123

    Good luck,


    • #3
      Re: setup ospf over frame relay in packet tracer

      Works like a charm...thank you Jules

      so the default for non-broadcast is 30 and "ip ospf network broadcast"
      changes the hello time to 10 seconds?
      you wrote that it tricks itself into thinking its on broadcast but when i ran "ip ospf int s0/1/0" without running "ip ospf network broadcast" it showed 30 seconds multipoint..

      also, when i changed it in router2 from "ip ospf network broadcast" into "ip ospf network point-to-point" the hello timers were the same (10 seconds) and i could see the neighbor but "sh ip route" didn't show the routes to R1 fa (and it did show them when it was on"ip ospf network broadcast"...why is that?

      another question...on frame relay topology,
      if one router uses sub-interfaces and the other is should work without any problems?

      once again, thank you very much for your help!


      • #4
        Re: setup ospf over frame relay in packet tracer


        Its complicated because Frame Relay is Non Broadcast Multi-Access (NBMA), whereas OSPF broadcasts and multicasts. So the broadcast type is a workaround. But it was only a partial workaround.

        Cisco recommends, "In a Frame Relay environment, if Layer 2 is unstable, as in our example, we do not recommend an OSPF broadcast network-type. Use OSPF point-to-multipoint instead."

        Since Packet Tracer is missing the neighbor and no frame-relay inverse-arp commands it's not surprising that point-to-multipoint is also missing.

        R3(config)#interface Serial0/0/0.31 ?
        multipoint Treat as a multipoint link
        point-to-point Treat as a point-to-point link

        I was unable to duplicate the output I provided earlier so I'm giving up using Packet Tracer for the CCNA OSPF Frame Relay portion. I spent way too much time trying to figure out a workaround to use the workarounds.

        If someone has a rock solid .pka, .pkz, or .pkt file for demonstrating OSPF running over Frame Relay with a hub using no sub-interfaces, a spoke with mulit-point, and a spoke with point-to-point I'd sure like to see it.

        GNS3 isn't nearly as convenient to initially setup as Packet Tracer, but at least you'll get the OSPF over Frame Relay routing commands you need. You'll also learn how to TFTP your IOS from old routers you bought from eBay and Craigs List.


        • #5
          Re: setup ospf over frame relay in packet tracer

          Hey Jules,

          thank you for your reply.

          GNS3 works fine, also with ospf over frame relay.
          the problem is the high amount of cpu and mem usage,
          even when i'm using idle-pc.
          I guess there is no other choise because packet tracer lacks these features.

          yet it should work if you setup point-to-point sub-interfaces on the hub for each spoke, the problem is they have to be on different subnets.

          Another problem that occurred to me - split horizon is disabled by default
          on frame relay interfaces but not on sub-interfaces.
          lets say you configure one hub and two spokes and the hub has
          a multi-point subinterface connected to the other two spokes.
          you cant use distance-vector protocol like eigrp because split horizon will
          not allow routing updates to reach from one spoke to another.
          you can't disable split horizon for eigrp in packet tracer.

          My question is, I don't understand how sub-interfaces should solve split horizon problems like this, I mean, If its disabled for interfaces but enabled for multipoint sub-interfaces then how come it's solving anything?