Frame relay and neighbor statements with ospf

MrXpertMrXpert Posts: 586Member
I setup a FRAME RELAY NETWORK between three routers, R1, R2,R3. Full mesh using only the physical interfaces on 192.168.0.0/29 subnet.They could ping each other.So i stepped up a gear and added loopback IPs to all the routers. I set the OSPF priority on R1 on its s0/0 as 200(i wanted R1 to be the big daddy). R2 AND R3 are default 1. I tried getting neighbor adjacency working but it didn't work. After some head stratching I realised this was being reported as a NBMA network by the show ip ospf int command. Even though I had added the word "broadcast" at the end of my frame map ip statements it still didn't help. Not sure why not? i thought the broadcast word was like a quasi broadcast thing? a solution but no...?

Anyway I then added the command "neighbor 192.168.0.2 priority 1" to R1 and it formed an adjaceny with R2.:) I did the same for R3. All seems to be working but I am a bit confused about the neighbor command in config-router mode.
Is it recommended to type neighbor statements on each router and also set the priority of the neighbor at the end of the command? it didn't seem to matter much either way as it worked and R1 became the DR, R3=BDR (probably because its ROUTER-ID was 3.3.3.3) and R2 was a drother. But i would like to know if what I did was right and if anyone can clarify anything that I might have misunderstood?

Am using GNS3.
I'm an Xpert at nothing apart from remembering useless information that nobody else cares about.

Comments

  • mattaumattau Posts: 218Member
    ospf and all the network types takes some getting used to :)

    basically nbma doesnt allow multicast so the frame relay maps dont really matter if broadcast word is on or not. Its irrelevant seems unicast are only permitted over the frame cloud - hence you have to manually say send unicast hellos to this neighbor under ospf router config mode.

    the key with the frame broadcast maps is you only need them if you are in any ospf network mode that allows dynamic neighbor discovery in the way of multicasts to 224.0.0.5 - such as point to multipoint and broadcast

    from the videos ive watched most ccie instructors say configure the priority to 0 on the spokes vs the neighbor command on the hub as its more consistent and guaranteed to work - so i just do what they say : P
    _____________________________________
    CCNP ROUTE - passed 20/3/12
    CCNP SWITCH - passed 25/10/12
    CCNP TSHOOT - passed 11/12/12




  • wavewave Posts: 342Member
    MrXpert wrote: »
    Is it recommended to type neighbor statements on each router and also set the priority of the neighbor at the end of the command?

    Technically you only need the neighbor statement on one of the routers, but best practice is to have them on both.

    mattau is right, OSPF network types are a lot of fun. It took me a solid couple of weeks of reading and labbing to grasp everything properly.

    I found Joe Astorino's blog posts on the subject extremely helpful:

    OSPF over Frame-Relay Part 1 Non-broadcast
    OSPF over Frame-Relay Part 2 Broadcast
    OSPF over Frame-Relay – Part 3: Point-To-Point
    OSPF over Frame-Relay – Part 4: Point-To-Multipoint
    OSPF over Frame-Relay – Part 5: Point-To-Multipoint Nonbroadcast
    OSPF over Frame-Relay Troubleshooting

    ROUTE Passed 1 May 2012
    SWITCH Passed 25 September 2012
    TSHOOT Passed 23 October 2012
    Taking CCNA Security in April 2013 then studying for the CISSP
  • MrXpertMrXpert Posts: 586Member
    Thanks guys! I see what you mean. OSPF is fun!:D i fiddled about with network types and had originally a partial mesh between 3 routers, p2p interfaces on each with one of them the hub. I then changed it so that between a pair of routers they'd be using NBMA and neighbor statements. I also altered the priorities to ensure the hub was the DR.
    So basically I had s1/0.1 and s1/0.2 p2p interfaces on the hub but s1/0.2 was a NBMA network
    I'm sure this is not a normal network design but it did get me used to understanding stuff a bit better.
    I'm an Xpert at nothing apart from remembering useless information that nobody else cares about.
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