【old】OSPF Loopback Prefix

※noteから引っ越してきた記事※

Before

iosv-3#sh ip o int bri 
Interface    PID   Area            IP Address/Mask    Cost  State Nbrs F/C
Lo0          1     0               3.3.3.3/8          1     LOOP  0/0
Gi0/0        1     0               192.168.23.3/24    1     BDR   1/1

iosv-0#sh ip ro 3.3.3.3
Routing entry for 3.3.3.3/32
  Known via "ospf 1", distance 110, metric 3, type intra area
  Last update from 192.168.12.2 on GigabitEthernet0/0, 00:24:56 ago
  Routing Descriptor Blocks:
  * 192.168.12.2, from 3.3.3.3, 00:24:56 ago, via GigabitEthernet0/0
      Route metric is 3, traffic share count is 1

Config

iosv-3(config-if)#int lo0
iosv-3(config-if)#ip o net point-to-po

After

iosv-3#sh ip o int bri
Interface    PID   Area            IP Address/Mask    Cost  State Nbrs F/C
Lo0          1     0               3.3.3.3/8          1     P2P   0/0
Gi0/0        1     0               192.168.23.3/24    1     BDR   1/1

iosv-0#sh ip ro
*Aug 30 13:54:48.025: %SYS-5-CONFIG_I: Configured from console by console
iosv-0#sh ip ro 3.3.3.3
Routing entry for 3.0.0.0/8
  Known via "ospf 1", distance 110, metric 3, type intra area
  Last update from 192.168.12.2 on GigabitEthernet0/0, 00:00:52 ago
  Routing Descriptor Blocks:
  * 192.168.12.2, from 3.3.3.3, 00:00:52 ago, via GigabitEthernet0/0
      Route metric is 3, traffic share count is 1

network type Loopbackには戻せない

iosv-3(config-if)#ip o net ?
  broadcast            Specify OSPF broadcast multi-access network
  non-broadcast        Specify OSPF NBMA network
  point-to-multipoint  Specify OSPF point-to-multipoint network
  point-to-point       Specify OSPF point-to-point network

iosv-3(config-if)#ip o net loopback
                           ^
% Invalid input detected at '^' marker.

というかpoint-to-point以外選択肢がない

iosv-3(config-if)#ip o net broadcast 
% OSPF: Invalid type for interface Loopback0

iosv-3(config-if)#ip o net point-to-multipoint 
% OSPF: Invalid type for interface Loopback0

iosv-3(config-if)#ip o net non-broadcast 
% OSPF: Invalid type for interface Loopback0

/32に戻す

iosv-3(config-if)#no ip  o  net po

iosv-3#sh ip o int bri
Interface    PID   Area            IP Address/Mask    Cost  State Nbrs F/C
Lo0          1     0               3.3.3.3/8          1     LOOP  0/0
Gi0/0        1     0               192.168.23.3/24    1     BDR   1/1

iosv-0#sh ip ro 3.3.3.3
Routing entry for 3.3.3.3/32
  Known via "ospf 1", distance 110, metric 3, type intra area
  Last update from 192.168.12.2 on GigabitEthernet0/0, 00:00:49 ago
  Routing Descriptor Blocks:
  * 192.168.12.2, from 3.3.3.3, 00:00:49 ago, via GigabitEthernet0/0
      Route metric is 3, traffic share count is 1

参考

CCIE Enterprise Infrastructure Foundation, 2nd Edition

1.4 OSPF (v2 and v3)