Configuring OSPF Route Summarization
Configuring OSPF route Summarization or the Open Shortest Path First (OSPFv3) for IPv6 on an interface has the same process for route summarization or aggregating IPv4 routes occurs with IPv6 routes, and the format is identical except that the configuration is placed under the IPv6 address family using the command aggregate-address prefix/prefix-length [summary-only] [as-set].
The ability to summarize IPv6 networks is as important as summarizing routes in IPv4 (and it may even be more important, due to hardware scale limitations).
OSPF Router Configuration
Router# show ipv6 route ospf | begin Application lA - LISP away, a - Application OI 2001:DB8::1/128 [110/3] via FE80::3, GigabitEthernet0/3 OI 2001:DB8::2/128 [110/2] via FE80::3, GigabitEthernet0/3 OI 2001:DB8::3/128 [110/1] via FE80::3, GigabitEthernet0/3 OI 2001:DB8:0:1::/64 [110/4] via FE80::3, GigabitEthernet0/3 OI 2001:DB8:0:12::/64 [110/3] via FE80::3, GigabitEthernet0/3 OI 2001:DB8:0:23::/64 [110/2] via FE80::3, GigabitEthernet0/3
Summarizing the Area 0 router’s loopback interfaces (2001:db8:0::1/128, 2001:db8:0::2/128, and 2001:db8:0::3/128) removes three routes from the routing table.
NOTE: A common mistake with OSPF summarization of IPv6 addresses is to confuse hex with decimal. We typically perform summarization logic in decimal, and the first and third digits in an octet should not be confused as decimal values. For example, the IPv6 address 2001::1/128 is not 20 and 1 in decimal format. The number 2001::1/128 is 32 and 1.
Configuring OSPF route Summarization of internal OSPFv3 routes follows the same rules as in OSPFv2 and must occur on ABRs. In our topology, R3 summarizes the three loopback addresses into the 2001:db8:0:0::/65 network. Summarization involves the command area area-id range prefix/ prefix-length, which resides under the address family in the OSPFv3 process. summary route summarize routes summary address summary routes router configuration mode advertise summary route show ip route default route ospf router automatic summarization routing tables directly connected ip addresses routing table route summarization summarize external routes routing loops
Router1# configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router1(config)# router ospfv3 1 Router1(config-router)# address-family ipv6 unicast Router1(config-router-af)# area 0 range 2001:db8:0:0::/65 Router# show ipv6 route ospf | begin Application lA - LISP away, a - Application OI 2001:DB8::/65 [110/4] via FE80::3, GigabitEthernet0/3 OI 2001:DB8:0:1::/64 [110/4] via FE80::3, GigabitEthernet0/3 OI 2001:DB8:0:12::/64 [110/3] via FE80::3, GigabitEthernet0/3 OI 2001:DB8:0:23::/64 [110/2] via FE80::3, GigabitEthernet0/3
OSPFv3 Route Summarization Passive Interface
OSPFv3 supports the ability to mark an interface as passive. The command is placed under the OSPFv3 process or under the specific address family. Placing the command under the global process cascades the setting to both address families. An interface is marked as being passive with the command passive-interface interface-id or globally with passive-interface default, and then the interface is marked as active with the command no passive-interface interface-id.
Router2(config)# router ospfv3 1 Router2(config-router)# passive-interface fastethernet0/0 Router(config)# router ospfv3 1 Router(config-router)# passive-interface default 22:10:46.838: %OSPFv3-5-ADJCHG: Process 1, IPv6, Nbr 192.168.3.3 on GigabitEthernet0/3 from FULL to DOWN, Neighbor Down: Interface down or detached Router(config-router)# no passive-interface GigabitEthernet 0/3
The active/passive state of an interface is verified by examining the OSPFv3 interface status using the command show ospfv3 interface [interface-id] and searching for the Passive keyword.
R1# show ospfv3 interface gigabitEthernet 0/1 | include Passive No Hellos (Passive interface)
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