7.3.6 RIP と IGRP でのデフォルトルーティング

基本設定、ripの設定後の show ip route

[Router0]

R 192.168.1.0/24 [120/1] via 192.168.2.1, 00:00:12, Serial2/0
C 192.168.2.0/24 is directly connected, Serial2/0

C 192.168.3.0/24 is directly connected, FastEthernet0/0

R 192.168.4.0/24 [120/1] via 192.168.2.1, 00:00:12, Serial2/0

R 192.168.5.0/24 [120/2] via 192.168.2.1, 00:00:12, Serial2/0

[Router1]

C 192.168.1.0/24 is directly connected, Serial2/0

C 192.168.2.0/24 is directly connected, Serial3/0

R 192.168.3.0/24 [120/1] via 192.168.2.2, 00:00:20, Serial3/0

C 192.168.4.0/24 is directly connected, FastEthernet0/0

R 192.168.5.0/24 [120/1] via 192.168.1.2, 00:00:05, Serial2/0

[Router2]

C 192.168.1.0/24 is directly connected, Serial2/0

R 192.168.2.0/24 [120/1] via 192.168.1.1, 00:00:09, Serial2/0

R 192.168.3.0/24 [120/2] via 192.168.1.1, 00:00:09, Serial2/0

R 192.168.4.0/24 [120/1] via 192.168.1.1, 00:00:09, Serial2/0

C 192.168.5.0/24 is directly connected, FastEthernet0/0

この後、Router0にloopback0とデフォルトルートをつけます。

(config)# ip route 0.0.0.0 0.0.0.0 loopback0

RIPでデフォルトルートを伝播させます。

(config)#router rip

(config-router)#default-information originate

#show ip route

[Router0]

C 172.16.1.1 is directly connected, Loopback0

R 192.168.1.0/24 [120/1] via 192.168.2.1, 00:00:04, Serial2/0

C 192.168.2.0/24 is directly connected, Serial2/0

C 192.168.3.0/24 is directly connected, FastEthernet0/0

R 192.168.4.0/24 [120/1] via 192.168.2.1, 00:00:04, Serial2/0

R 192.168.5.0/24 [120/2] via 192.168.2.1, 00:00:04, Serial2/0

S* 0.0.0.0/0 is directly connected, Loopback0

[Router1]

C 192.168.1.0/24 is directly connected, Serial2/0

C 192.168.2.0/24 is directly connected, Serial3/0

R 192.168.3.0/24 [120/1] via 192.168.2.2, 00:00:00, Serial3/0

C 192.168.4.0/24 is directly connected, FastEthernet0/0

R 192.168.5.0/24 [120/1] via 192.168.1.2, 00:00:10, Serial2/0

R* 0.0.0.0/0 [120/1] via 192.168.2.2, 00:00:00, Serial3/0

[Router2]

C 192.168.1.0/24 is directly connected, Serial2/0

R 192.168.2.0/24 [120/1] via 192.168.1.1, 00:00:13, Serial2/0

R 192.168.3.0/24 [120/2] via 192.168.1.1, 00:00:13, Serial2/0

R 192.168.4.0/24 [120/1] via 192.168.1.1, 00:00:13, Serial2/0

C 192.168.5.0/24 is directly connected, FastEthernet0/0

R* 0.0.0.0/0 [120/2] via 192.168.1.1, 00:00:13, Serial2/0

これで、どのワークステーションからも172.16.1.1 にpingできます。

7.2.7インタフェース経由のルーティング更新の抑止

両ルータにripを設定後のshow ip route

[router0]
C 192.168.14.0/24 is directly connected, FastEthernet0/0
C 192.168.15.0/24 is directly connected, Serial2/0
R 192.168.16.0/24 [120/1] via 192.168.15.2, 00:00:04, Serial2/0

[router1]
C 192.168.14.0/24 is directly connected, FastEthernet0/0
C 192.168.15.0/24 is directly connected, Serial2/0
R 192.168.16.0/24 [120/1] via 192.168.15.2, 00:00:04, Serial2/0

この状態でPC0⇔PC1のpingは通ります。
ここでRouter0からRouter1への更新を中止します。
Router0#(config-route)#passive-interface serial 0

（しばらく待って）この状態でのshow ip route
[Router0]
C 192.168.14.0/24 is directly connected, FastEthernet0/0
C 192.168.15.0/24 is directly connected, Serial2/0
R 192.168.16.0/24 [120/1] via 192.168.15.2, 00:00:18, Serial2/0

[Router1]
C 192.168.15.0/24 is directly connected, Serial2/0
C 192.168.16.0/24 is directly connected, FastEthernet0/0

PC0⇒PC1 のping : time out
PC1⇒PC0 のping : Destination host unreachable.
となり届かない。unreachableはルーティングテーブルがないこと。
更新情報がいかないので、ルーティングテーブルからRが削除

Router1にデフォルトルートを設定
(config)# ip route 0.0.0.0 0.0.0.0 192.168.15.1

[Router1] show ip route
C 192.168.15.0/24 is directly connected, Serial2/0
C 192.168.16.0/24 is directly connected, FastEthernet0/0
S* 0.0.0.0/0 [1/0] via 192.168.15.1

スタティックデフォルトルートが追加されている。
Router0⇔Router1 のpingが通るようになる