HELP!!! routers wont form neighbours

kelsnjokukelsnjoku Posts: 2Registered Users ■□□□□□□□□□
hello there..

I am trying to set up a single area OSPF routing network but BB1 and R1 (see picture and PT file below) wont form neighbors in other to exchange route information. Other routers in the network are working fine and exchanging routes.

I have checked, and both mentioned routers are in the same area (area 0) and have both link ends in the same subnet. Why they have refused to exchange routes is beyond me.

Someone please troubleshoot and let me know what's wrong. I would also love to know how to use the debug command: debug ip ospf adj.

please find below the configuration of both routers in question.

BB1
hostname BB1
...
interface FastEthernet0/0
ip address 172.16.10.254 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
ip address 172.16.11.254 255.255.255.0
duplex auto
speed auto
!
interface Serial0/0/0
ip address 10.1.1.100 255.255.255.0
....
!
router ospf 1
log-adjacency-changes
network 10.1.1.0 0.0.0.255 area 0
network 172.16.0.0 0.0.255.255 area 0
!
ip classless

R1
!
hostname R1
...
interface Serial0/0/0
ip address 192.168.1.17 255.255.255.240
clock rate 64000
!
interface Serial0/1/0
ip address 192.168.1.33 255.255.255.240
clock rate 64000
!
interface Serial0/2/0
ip address 192.168.1.49 255.255.255.240
clock rate 64000
!
interface Serial0/3/0
ip address 10.1.1.1 255.255.255.0
clock rate 64000
...
router ospf 1
log-adjacency-changes
network 10.1.1.1 0.0.0.0 area 0
network 192.168.0.0 0.0.255.255 area 0
...
end

Comments

  • networker050184networker050184 Posts: 11,962Mod Mod
    Is the interface up? Can you ping across?

    How you use the debug is just type in the command.
    An expert is a man who has made all the mistakes which can be made.
  • RouteMyPacketRouteMyPacket Posts: 1,104Member
    On R1 under the OSPF process, do the following and see what you get

    router ospf 1
    no network 10.1.1.1 0.0.0.0 area 0
    network 10.1.1.0 0.0.0.255 area 0
    Modularity and Design Simplicity:

    Think of the 2:00 a.m. test—if you were awakened in the
    middle of the night because of a network problem and had to figure out the
    traffic flows in your network while you were half asleep, could you do it?
  • kMastaFlashkMastaFlash GXPN,GWAPT,GPEN,GCIH,GNFA ++ Posts: 1,019Member ■■■■■□□□□□
    Have you tried a show cdp neighbors, show ip ospf border-routers, or show ip ospf? Post those configs here.
    2019: CCNA Security,CTIA,JNCDA
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  • MAC_AddyMAC_Addy Posts: 1,740Member ■■■■□□□□□□
    Oh, RouteMyPacket, you beat me to it.
    2017 Certification Goals:
    CCNP R/S
  • networker050184networker050184 Posts: 11,962Mod Mod
    On R1 under the OSPF process, do the following and see what you get

    router ospf 1
    no network 10.1.1.1 0.0.0.0 area 0
    network 10.1.1.0 0.0.0.255 area 0


    That doesn't matter. As long as it matches the interface it's fine. It is actually my preferred method to always use a 0.0.0.0 mask with OSPF.
    An expert is a man who has made all the mistakes which can be made.
  • GngoghGngogh Posts: 160Member ■■■□□□□□□□
    Just to clarify something... you have changed the network statement and the routers were able to perform adjacency ???

    If so, its a bit wierd to me, because from what i know from OSPF the wildcard in the network statement as no influence in the mask address that is sent in hello packets.

    I have done a little topology with 2 routers.

    router0 - network 10.1.1.100 0.0.0.255 area 0

    router1 - network 10.1.1.1 0.0.0.0 area 0

    and the routers perform adjacency...
  • networker050184networker050184 Posts: 11,962Mod Mod
    You are correct Gngogh, the network command only matches on an interface IP. It has no influence what subnet mask is used.

    This is one of my biggest pet peeves that people seem to misunderstand. I had to argue with a CCIE from Cisco TAC for about 20 minutes about this a few months ago. He was convinced that an all 0 mask would not work even though it is configured all over our (and many other) networks......
    An expert is a man who has made all the mistakes which can be made.
  • Dieg0MDieg0M Posts: 861Member
    networker is correct, in OSPF the mask of the network statement only influences the local interfaces in the up/up state that will form neighborship. It is the same for RIP and EIGRP. Only BGP will use the network mask in the network statement.
    Follow my CCDE journey at www.routingnull0.com
  • GngoghGngogh Posts: 160Member ■■■□□□□□□□
    So the question remains, why the routers were not performing full adjacency????
  • RouteMyPacketRouteMyPacket Posts: 1,104Member
    Gngogh wrote: »
    So the question remains, why the routers were not performing full adjacency????

    Buggy perhaps? I would have added the command I posted above to check but as stated above it absolutely should not matter and his original statements should allow the adjacency to form between BB1 and R1. PT has issues so I wouldn't be shocked if this is one of them, HSRP for example has a major bug in PT.
    Modularity and Design Simplicity:

    Think of the 2:00 a.m. test—if you were awakened in the
    middle of the night because of a network problem and had to figure out the
    traffic flows in your network while you were half asleep, could you do it?
  • lsud00dlsud00d Posts: 1,571Member
    Dieg0M wrote: »
    networker is correct, in OSPF the mask of the network statement only influences the local interfaces in the up/up state that will form neighborship. It is the same for RIP and EIGRP. Only BGP will use the network mask in the network statement.

    *makes note*
  • JeanMJeanM Posts: 1,117Member
    Good tips here!
    2015 goals - ccna voice / vmware vcp.
  • kelsnjokukelsnjoku Posts: 2Registered Users ■□□□□□□□□□
    when i entered the debug command, nothing happened (when routers couldn't form neighbors). I am yet to understand what that command really achieves though.

    @all, surprisingly, BB1 and R1 have formed OSPF neighbors now and everything is working fine. I didn't change anything, I only restarted PT. I suspect the inability of the routers to form neighbors was an issue with PT just as RouteMyPacket hinted. I am now considering GNS3 for my practice even though I kind of find it daunting using GNS3.

    thanks everyone for your input
  • MAC_AddyMAC_Addy Posts: 1,740Member ■■■■□□□□□□
    GNS3 is brilliant, in my opinion. Though, it does take a little setting up. Mostly all issues are reported on their forums, so if you run into anything a quick google search will have you pointed in the right direction. Once you have it said and done it's amazing.
    2017 Certification Goals:
    CCNP R/S
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