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DES-7200 Configuration Guide Chapter 4 OSPF
Configuration
4-59
2. During route summarization, the summarized range may exceed the actual
network range in the routing table. Routing loop may incur or the burden of router
may be increased if packets are sent to a nonexistent network. To avoid this, we
need to add a "discard" route to the routing table of ABR (Switch B) or ASBR, so
as to add the "discard" routes generated by the inter-area route summarization
command of "area range". This feature is enabled by default.
3. The summary address of 172.16.1.0/24, 172.16.2.0/24, 172.16.3.0/24 and
172.16.4.0/24 is 172.16.0.0/21. Routes falling within this range won't be
advertised to other areas by ABR.
Configuration Steps
Step 1: Configure the IP address of respective interfaces (omitted)
Step 2: Configure OSPF basic features
Configure Switch A
SwitchA(config)#router ospf 1
SwitchA(config)# network 192.168.12.0 0.0.0.255 area 0
Configure Switch B
SwitchB(config)#router ospf 1
SwitchB(config-router)#network 192.168.12.0 0.0.0.255 area 0
SwitchB(config-router)#network 172.16.1.0 0.0.0.255 area 2
SwitchB(config-router)#network 172.16.2.0 0.0.0.255 area 2
Configure Switch C
SwitchC(config)#router ospf 1
SwitchC(config-router)#network 172.16.1.0 0.0.0.255 area 2
SwitchC(config-router)#network 172.16.3.0 0.0.0.255 area 2
Configure Switch D
SwitchD(config)#router ospf 1
SwitchD(config-router)#network 172.16.2.0 0.0.0.255 area 2
SwitchD(config-router)#network 172.16.4.0 0.0.0.255 area 2
Display OSPF routing table of Switch A
SwitchA#show ip route ospf
O IA 172.16.1.0/24 [110/2] via 192.168.12.2, 00:06:47, GigabitEthernet 0/1
O IA 172.16.2.0/24 [110/2] via 192.168.12.2, 00:06:47, GigabitEthernet 0/1
O IA 172.16.3.0/24 [110/3] via 192.168.12.2, 00:06:47, GigabitEthernet 0/1
O IA 172.16.4.0/24 [110/3] via 192.168.12.2, 00:06:19, GigabitEthernet 0/1