Summarize Inter-Area and External Routes
Figure 5-37 shows the configuration to enable inter-area and external route summarization. The IPv4 address family is enabled on R1. R2 summarizes the internal OSPF routes which R3 redistributes.
Topology
Figure 5-37: Enabling Intra-Area and External Route Summarization
Configuration
R1
#configure terminal | Enter configure mode. |
(config)#router ipv6 ospf 100-ABC | Configure the routing process and specify the tag (100-ABC) which uniquely identifies the routing process |
(config-router)#router-id 10.12.49.123 | Configure the router ID to use for this process. |
(config-router)#exit | Exit OSPF router mode |
(config)#interface eth1 | Enter interface mode |
(config-if)#ip address 10.10.10.1/24 | Specify IP address for interface eth1 |
(config-if)#ipv6 router ospf area 0 tag 100-ABC instance-id 31 | Configure the interface in an area assigned with the area ID (0) which uniquely identifies the routing process and the instance identifier which is 0-31 for the IPv6 address family. |
(config-if)#commit | Commit the candidate configuration to the running configuration. |
R2
#configure terminal | Enter configure mode. |
(config)#router ipv6 ospf 100-ABC | Configure the routing process and specify the tag (100-ABC) which uniquely identifies the routing process |
(config-router)#router-id 10.12.49.124 | Configure the router ID to use for this process |
(config-router)#exit | Exit OSPF router mode |
(config)#interface eth1 | Enter interface mode |
(config-if)#ip address 10.10.10.2/24 | Specify an IP address for the interface |
(config-if)#ipv6 router ospf area 0 tag 100-ABC instance-id 31 | Configure the interface in an area assigned with the area ID (0) which uniquely identifies the routing process and the instance identifier which is 0-31 for the IPv4 address family. |
(config-if)#exit | Exit interface mode |
(config)#interface eth2 | Enter interface mode |
(config-if)#ip address 20.20.20.1/24 | Specify an IP address for the interface |
(config-if)#ipv6 router ospf area 1 tag 100-ABC instance-id 30 | Configure the interface in an area assigned with the area ID (1) which uniquely identifies the routing process and the instance identifier which is 0-31 for the IPv6 address family. |
(config-if)#exit | Exit interface mode |
(config)#interface lo | Enter interface mode |
(config-if)#ipv6 router ospf area 1 tag 101 instance-id 30 | Configure the interface in an area assigned with the area ID (1) which uniquely identifies the routing process and the instance identifier which is 0-31 for the IPv6 address family. |
(config-if)#commit | Commit the candidate configuration to the running configuration. |
(config-if)#exit | Exit interface mode |
R3
#configure terminal | Enter configure mode. |
(config)#router ipv6 ospf 100-ABC | Configure the routing process and specify the tag (100-ABC) which uniquely identifies the routing process |
(config-router)#router-id 10.12.49.125 | Configure the router ID to use for this process |
(config-router)#exit | Exit OSPF router mode |
(config)#interface eth1 | Enter interface mode |
(config-if)#ip address 20.20.20.2/24 | Specify an IP address for the interface |
(config-if)#ipv6 router ospf area 1 tag 100-ABC instance-id 30 | Configure the interface in an area assigned with the area ID (1) which uniquely identifies the routing process and the instance identifier which is 0-31 for the IPv4 address family. |
(config-if)#commit | Commit the candidate configuration to the running configuration. |
(config-if)#exit | Exit interface mode |
Validation
Validation 1: Verify that adjacency has been established with the configured instance identifier.
R2#show ipv6 ospf neighbor
OSPFv3 Process (100-ABC)
Neighbor ID Pri State Dead Time Interface Instance ID
10.12.49.123 1 Full/Backup 00:00:38 eth1 31
10.12.49.125 1 Full/DR 00:00:38 eth2 30
Validation 2: Verify that a single summarized OSPF IA route and a single summarized external route is available in FIB of R1
R1#show ip route
Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2,
ia - IS-IS inter area, E - EVPN,
v - vrf leaked
* - candidate default
IP Route Table for VRF "default"
C 10.0.0.0/8 is directly connected, eth0, 00:45:18
C 11.1.1.0/24 is directly connected, eth1, 00:40:01
O IA 22.1.1.0/24 [110/2] via 11.1.1.2, eth1, 00:37:57
O IA 100.1.1.0/24 [110/2] via 11.1.1.2, eth1, 00:24:59
C 127.0.0.0/8 is directly connected, lo, 00:45:18
O E2 200.1.1.0/24 [110/20] via 11.1.1.2, eth1, 00:00:54
Gateway of last resort is not set
R1#
Validation 3: Verify that the Inter-Area Prefix LSA and External LSA in OSPFv3 database of R1 consists of just a single prefix 100.1.1.0/24 and 200.1.1.0/24 respectively
R1#show ipv6 ospf database inter-prefix
OSPFv3 Router with ID (10.12.49.123) (Process 100-ABC)
Inter-Area-Prefix-LSA (Area 0.0.0.0)
LS age: 771
LS Type: Inter-Area-Prefix-LSA
Link State ID: 0.0.0.1
Advertising Router: 10.12.49.124
LS Seq Number: 0x80000002
Checksum: 0x60E3
Length: 32
Metric: 1
Prefix: 22.1.1.0/24
Prefix Options: 0
LS age: 21
LS Type: Inter-Area-Prefix-LSA
Link State ID: 0.0.0.2
Advertising Router: 10.12.49.124
LS Seq Number: 0x80000008
Checksum: 0x489D
Length: 32
Metric: 1
Prefix: 127.0.0.0/8
Prefix Options: 0
LS age: 1795
LS Type: Inter-Area-Prefix-LSA
Link State ID: 0.0.0.5
Advertising Router: 10.12.49.124
LS Seq Number: 0x80000001
Checksum: 0x975B
Length: 32
Metric: 1
Prefix: 100.1.1.0/24
Prefix Options: 0
R1#
R1#show ipv6 ospf database external
OSPFv3 Router with ID (10.12.49.123) (Process 100-ABC)
AS-external-LSA
LS age: 390
LS Type: AS-External-LSA
Link State ID: 0.0.0.1
Advertising Router: 10.12.49.125
LS Seq Number: 0x80000001
Checksum: 0xCE5A
Length: 32
Metric Type: 2 (Larger than any link state path)
Metric: 20
Prefix: 10.0.0.0/8
Prefix Options: 0 (-|-|-|-)
LS age: 364
LS Type: AS-External-LSA
Link State ID: 0.0.0.4
Advertising Router: 10.12.49.125
LS Seq Number: 0x80000001
Checksum: 0x6CE8
Length: 32
Metric Type: 2 (Larger than any link state path)
Metric: 20
Prefix: 200.1.1.0/24
Prefix Options: 0 (-|-|-|-)
R1#
Validation 4: Verify that a single summarized external route is present in the ABR R2
R2#show ip route
Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2,
ia - IS-IS inter area, E - EVPN,
v - vrf leaked
* - candidate default
IP Route Table for VRF "default"
C 10.0.0.0/8 is directly connected, eth0, 00:55:15
C 11.1.1.0/24 is directly connected, eth1, 00:49:17
C 22.1.1.0/24 is directly connected, eth2, 00:48:18
O 100.1.1.0/24 [110/0] is a summary, Null, 00:35:05
C 100.1.1.100/32 is directly connected, lo, 00:35:40
C 100.1.1.110/32 is directly connected, lo, 00:35:36
C 127.0.0.0/8 is directly connected, lo, 00:55:15
O E2 200.1.1.0/24 [110/20] via 22.1.1.2, eth2, 00:11:00
Gateway of last resort is not set
R2#
Validation 5: Verify that the Type 5 LSA in the ABR's Link State Data Base consistes of just a single prefix 200.1.1.0/24
R2#show ipv6 ospf database external
OSPFv3 Router with ID (10.12.49.124) (Process 100-ABC)
AS-external-LSA
LS age: 774
LS Type: AS-External-LSA
Link State ID: 0.0.0.1
Advertising Router: 10.12.49.125
LS Seq Number: 0x80000001
Checksum: 0xCE5A
Length: 32
Metric Type: 2 (Larger than any link state path)
Metric: 20
Prefix: 10.0.0.0/8
Prefix Options: 0 (-|-|-|-)
LS age: 748
LS Type: AS-External-LSA
Link State ID: 0.0.0.4
Advertising Router: 10.12.49.125
LS Seq Number: 0x80000001
Checksum: 0x6CE8
Length: 32
Metric Type: 2 (Larger than any link state path)
Metric: 20
Prefix: 200.1.1.0/24
Prefix Options: 0 (-|-|-|-)
Last modified date: 07-13-2023