Why do we need to create a virtual-link between R8 and
Sw1 through Vlan80?
When I bring down R6's S0/2/0 and s0/2/1, R8 still has
its neighbor relationship with SW1 via Area 80 and Sw
1 is connected to Area 0. Look at the route table
from R8 below after taking down R6's serials. R8
still has all the backbone routes.
R8 sh ip os nei
Neighbor ID Pri State Dead Time
Address Interface
50.51.0.11 1 FULL/BDR 00:00:38
50.51.80.11 FastEthernet0/0
50.51.0.7 0 FULL/ - 00:00:39
50.51.0.7 Serial0/0/0
R8(config)#sir os
50.0.0.0/8 is variably subnetted, 17 subnets, 5
masks
O E1 50.51.0.2/32 [110/1066] via 50.51.80.11,
00:00:02, FastEthernet0/0
O IA 50.51.5.0/24 [110/2] via 50.51.80.11,
01:07:29, FastEthernet0/0
O IA 50.51.0.5/32 [110/3] via 50.51.80.11,
00:53:08, FastEthernet0/0
O IA 50.51.0.6/32 [110/67] via 50.51.80.11,
00:52:48, FastEthernet0/0
O IA 50.51.0.9/32 [110/66] via 50.51.0.7, 00:00:07,
Serial0/0/0
O IA 50.51.0.11/32 [110/2] via 50.51.80.11,
00:52:00, FastEthernet0/0
O E1 50.51.0.12/32 [110/1067] via 50.51.80.11,
00:00:02, FastEthernet0/0
O E1 50.51.22.0/24 [110/1067] via 50.51.80.11,
00:00:02, FastEthernet0/0
O E1 50.51.24.0/24 [110/1066] via 50.51.80.11,
00:00:02, FastEthernet0/0
O IA 50.51.26.0/29 [110/130] via 50.51.80.11,
01:07:24, FastEthernet0/0
O IA 50.51.18.8/31 [110/129] via 50.51.0.7,
00:00:07, Serial0/0/0
O IA 50.51.26.5/32 [110/2] via 50.51.80.11,
01:07:24, FastEthernet0/0
O IA 50.51.66.0/24 [110/67] via 50.51.80.11,
00:09:08, FastEthernet0/0
O 50.51.79.0/25 [110/65] via 50.51.0.7,
01:14:57, Serial0/0/0
R8(config)#srbr
router ospf 1
log-adjacency-changes
network 50.51.0.8 0.0.0.0 area 789
network 50.51.80.0 0.0.0.255 area 80
