OSPF process id and DR selection

Discussion in 'Cisco' started by hscottk, Dec 7, 2009.

  1. hscottk

    hscottk

    Joined:
    Dec 7, 2009
    Messages:
    1
    Hello,

    I am studying for the CCNA and found an odd result in the lab for OSPF DR elections. I am using a 2621 and 2821 in the lab.

    Since we are told that the OSPF process id is only locally significant, I randomly chose two different numbers for the two routers (1 and 2). What I found was that the router with the process id of 1 always became the DR even when it had a lower router id. I even setup a loopback interface on the other router with a much higher IP address and still I got this result:

    Scott_Lab_Router1#sh ip ospf in
    GigabitEthernet0/0.2 is up, line protocol is up
    Internet Address 192.168.2.1/24, Area 0
    Process ID 2, Router ID 199.199.199.199, Network Type BROADCAST, Cost: 1
    Transmit Delay is 1 sec, State BDR, Priority 1
    Designated Router (ID) 192.168.3.10, Interface address 192.168.2.10
    Backup Designated router (ID) 199.199.199.199, Interface address 192.168.2.1
    Neighbor Count is 1, Adjacent neighbor count is 1
    Adjacent with neighbor 192.168.3.10 (Designated Router)
    Suppress hello for 0 neighbor(s)

    The other router......

    Scott_Lab_Router2#sh ip ospf int
    FastEthernet0/0 is up, line protocol is up
    Internet Address 192.168.2.10/24, Area 0
    Process ID 1, Router ID 192.168.3.10, Network Type BROADCAST, Cost: 1
    Transmit Delay is 1 sec, State DR, Priority 1
    Designated Router (ID) 192.168.3.10, Interface address 192.168.2.10
    Backup Designated router (ID) 199.199.199.199, Interface address 192.168.2.1
    Neighbor Count is 1, Adjacent neighbor count is 1
    Adjacent with neighbor 199.199.199.199 (Backup Designated Router)
    Suppress hello for 0 neighbor(s)


    As you can see, the priorities on both interfaces are 1, so that can't be the issue. And when I changed the process id from 1 to 2 on router 2 (so they were both the same) the correct DR elections came up (see below).

    Scott_Lab_Router2(config)#no router ospf 1
    Scott_Lab_Router2(config)#
    *Mar 1 01:09:01.311: %OSPF-5-ADJCHG: Process 1, Nbr 199.199.199.199 on FastEthe
    rnet0/0 from FULL to DOWN, Neighbor Down: Interface down or detached
    Scott_Lab_Router2(config)#router ospf 2
    Scott_Lab_Rout(config-router)#network 192.168.2.0 0.0.0.255 area 0
    Scott_Lab_Rout(config-router)#
    *Mar 1 01:09:19.235: %OSPF-5-ADJCHG: Process 2, Nbr 199.199.199.199 on FastEthe
    rnet0/0 from LOADING to FULL, Loading Done
    Scott_Lab_Rout(config-router)#network 192.168.3.0 0.0.0.255 area 0
    Scott_Lab_Rout(config-router)#^Z
    Scott_Lab_Router2#
    *Mar 1 01:09:38.019: %SYS-5-CONFIG_I: Configured from console by console
    Scott_Lab_Router2#sh ip ospf int
    FastEthernet0/0 is up, line protocol is up
    Internet Address 192.168.2.10/24, Area 0
    Process ID 2, Router ID 192.168.3.10, Network Type BROADCAST, Cost: 1
    Transmit Delay is 1 sec, State BDR, Priority 1
    Designated Router (ID) 199.199.199.199, Interface address 192.168.2.1
    Backup Designated router (ID) 192.168.3.10, Interface address 192.168.2.10
    Neighbor Count is 1, Adjacent neighbor count is 1
    Adjacent with neighbor 199.199.199.199 (Designated Router)

    Can someone tell me why this is? Nothing in the book talks about an OSPF process id overriding other configurations in the eleciton of a DR or BDR.

    Your help would be greatly appreciated
    Scott
     
    hscottk, Dec 7, 2009
    #1
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  2. hscottk

    donjohnston

    Joined:
    Jun 28, 2008
    Messages:
    38
    Sounds like a bug in the IOS to me.

    I would file it away for now and continue.
     
    donjohnston, Dec 28, 2009
    #2
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