Re: OSPF NBMA and Multipoint Beighbourship Issues

Point to mutipoint interfaces don't elect DR's. All the DR really does is
ensure that there is only one lsdb per subnet which is done here. Just
because the other router thinks there is no DR doesn't change the fact the
R1 has the full DB. I tried this in a lab once. I can't remember why the
routes disappear though. Do some debugs if you really want to know
what's going on. Since they are fully adjacent my guess is that they both
have the LSDB but there is something wrong with the LSA's themselves like
invalid next hops or sth. But that's just a guess of course. I'm sure
someone will correct me shortly.

Keegan

From:
Divin Mathew John <divinjohn_at_gmail.com>
To:
Cisco certification <ccielab_at_groupstudy.com>
Date:
07/13/2009 01:33 PM
Subject:
OSPF NBMA and Multipoint Beighbourship Issues
Sent by:
nobody_at_groupstudy.com

hello

I have this scenario.... R1------FR-Switch----R2

R1 to R2 102 Dlci
R2 to R1 DLCI 201

R1 config

interface Serial0/0
 ip address 12.1.1.1 255.255.255.0
 encapsulation frame-relay
 ip ospf network point-to-multipoint
 serial restart-delay 0
 frame-relay map ip 12.1.1.2 102 broadcast
!
router ospf 1
 log-adjacency-changes
 network 1.1.1.1 0.0.0.0 area 0
 network 12.1.1.1 0.0.0.0 area 0
 neighbor 12.1.1.2

R2 Config

interface Loopback0
 ip address 2.2.2.2 255.255.255.0
!
interface Serial0/0
 ip address 12.1.1.2 255.255.255.0
 encapsulation frame-relay
 ip ospf network non-broadcast
 serial restart-delay 0
 frame-relay map ip 12.1.1.1 201 broadcast
!
interface Serial0/1
 no ip address
 shutdown
 serial restart-delay 0
!
interface Serial0/2
 no ip address
 shutdown
 serial restart-delay 0
!
interface Serial0/3
 no ip address
 shutdown
 serial restart-delay 0
!
router ospf 1
 log-adjacency-changes
 network 2.2.2.2 0.0.0.0 area 0
 network 12.1.1.2 0.0.0.0 area 0
!

R1#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface
12.1.1.2 0 FULL/ - 00:01:32 12.1.1.2 Serial0/0

R1#sio int se0/0
Serial0/0 is up, line protocol is up
  Internet Address 12.1.1.1/24, Area 0
  Process ID 1, Router ID 12.1.1.1, Network Type POINT_TO_MULTIPOINT,
Cost:
64
  Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT,
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
    oob-resync timeout 120
    Hello due in 00:00:11
  Supports Link-local Signaling (LLS)
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 4 msec, maximum is 4 msec
  Neighbor Count is 1, Adjacent neighbor count is 1
    Adjacent with neighbor 12.1.1.2
  Suppress hello for 0 neighbor(s)

R2#show ip ospf neighbor
12.1.1.1 1 FULL/BDR 00:01:33 12.1.1.1 Serial0/0

R2#sio int se0/0
Serial0/0 is up, line protocol is up
  Internet Address 12.1.1.2/24, Area 0
  Process ID 1, Router ID 12.1.1.2, Network Type NON_BROADCAST, Cost: 64
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router (ID) 12.1.1.2, Interface address 12.1.1.2
  Backup Designated router (ID) 12.1.1.1, Interface address 12.1.1.1
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
    oob-resync timeout 120
    Hello due in 00:00:06
  Supports Link-local Signaling (LLS)
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 0 msec, maximum is 4 msec
  Neighbor Count is 1, Adjacent neighbor count is 1
    Adjacent with neighbor 12.1.1.1 (Backup Designated Router)
  Suppress hello for 0 neighbor(s)

Now the adjacency forms between R1 and R2 ...but routes aren't being
exchanged.. but adj stays up always..! According to what i have read, If a
network type wants DR/BDR election..it will only make neighbor with a
network type with DR/BDR election.. like NBMA and Broadcast are
compatible.
P-2-M and P2P are compatible... when timers are adjusted of course. But my
question why is NBMA forming neighbourship with P2M!?

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Received on Mon Jul 13 2009 - 14:09:55 ART