Hi all,
I had always assumed that it was only possible to have one DR in a single Area 0. If there were two routers with the same priority then the DR would get chosen on the basis of the highest mac. However tonight when doing a practise lab in GNS3 I am seeing two DR's in Area 0? Am i missing something here? The network is a standard broadcast network and routers Topaz and Quartz both have interfaces that are DR's on area 0. Attached is the topology and output is below:
On router Topaz you can see that interface Fa1/0 is the DR for Area 0:
Topaz#sh ip ospf int br
Interface PID Area IP Address/Mask Cost State Nbrs F/C
Fa1/0 100 0 192.168.12.2/24 1 DR 1/1
Fa0/0 100 1 192.168.23.2/24 1 DR 1/1
Topaz#sh ip ospf int fa1/0
FastEthernet1/0 is up, line protocol is up
Internet Address 192.168.12.2/24, Area 0
Process ID 100, Router ID 192.168.23.2, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 192.168.23.2, Interface address 192.168.12.2
Backup Designated router (ID) 192.168.14.1, Interface address 192.168.12.1
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:07
Supports Link-local Signaling (LLS)
Index 1/1, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 3, maximum is 3
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 192.168.14.1 (Backup Designated Router)
Suppress hello for 0 neighbor(s)
Topaz#sh run | b router ospf
router ospf 100
log-adjacency-changes
area 1 range 172.16.0.0 255.255.252.0
network 192.168.12.0 0.0.0.255 area 0
network 192.168.23.0 0.0.0.255 area 1
!
On router Quartz interface Fa0/0 is the DR for area 0:
Quartz#sh ip ospf int fa0/0
FastEthernet0/0 is up, line protocol is up
Internet Address 192.168.14.4/24, Area 0
Process ID 100, Router ID 192.168.45.4, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 192.168.45.4, Interface address 192.168.14.4
Backup Designated router (ID) 192.168.14.1, Interface address 192.168.14.1
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:01
Supports Link-local Signaling (LLS)
Index 1/1, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 0, maximum is 3
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 192.168.14.1 (Backup Designated Router)
Suppress hello for 0 neighbor(s)
Quartz#sh run | b router ospf
router ospf 100
log-adjacency-changes
area 2 range 10.10.0.0 255.255.248.0
network 192.168.14.0 0.0.0.255 area 0
network 192.168.45.0 0.0.0.255 area 2
!
