Configuration Example of OSPFv3 Route Summary [Cisco]

Table of Contents

Summary

This is a configuration example for summarizing OSPFv3 inter-area routes on Cisco router. The concept of the cost of summarized route is different for OSPFv3 than for OSPFv2 for IPv4.

Network Diagram

Configuration Condition

Enable OSPFv3 based on the network diagram.
Ensure that OSPFv3 routes are displayed as follows on R2.

R2#show ipv6 route ospf
IPv6 Routing Table - 10 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
       U - Per-user Static route
       I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
       O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
O   2000:12:12:12::/64 [110/10]
     via ::, Ethernet0/0
O   2001:3:3:1::/64 [110/20]
     via FE80::3, Ethernet0/1
O   2001:3:3:2::/64 [110/30]
     via FE80::3, Ethernet0/1
O   2001:3:3:3::/64 [110/40]
     via FE80::3, Ethernet0/1

Ensure that OSPFv3 routes are displayed as follows on R1.

R1#show ipv6 route ospf
IPv6 Routing Table - 7 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
       U - Per-user Static route
       I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
       O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
OI  2001:3:3::/48 [110/50]
     via FE80::2, Ethernet0/0
O   2001:12:12:12::/64 [110/10]
     via ::, Ethernet0/0
OI  2001:23:23:23::/64 [110/20]
     via FE80::2, Ethernet0/0

Initial Configuration

Hostname
IPv6 address

Configuration and Verification

Step1: Enable OSPFv3

Enable OSPFv3 on R1/R2/R3 based on the network diagram. In R3, the Loopback interface configures a network of 2001:3:3:1::/64, 2001:3:3:2::/64, and 2001:3:3:3::/64. The ipv6 ospf network point-to-point command is required on the R3 Loopback interfaces so that OSPF routes beginning with “2001:3:3” are visible with the configured subnet mask.

interface Ethernet0/0
 ipv6 ospf 1 area 0
!
ipv6 router ospf 1
 router-id 1.1.1.1

interface Ethernet0/0
 ipv6 ospf 1 area 0
!
interface Ethernet0/1
 ipv6 ospf 1 area 1
!
ipv6 router ospf 1
 router-id 2.2.2.2

interface Loopback0
 ipv6 ospf network point-to-point
 ipv6 ospf 1 area 1
!
interface Loopback1
 ipv6 ospf network point-to-point
 ipv6 ospf 1 area 1
!
interface Loopback2
 ipv6 ospf network point-to-point
 ipv6 ospf 1 area 1
!
interface Ethernet0/0
 ipv6 ospf 1 area 1
!
ipv6 router ospf 1
 router-id 3.3.3.3

Step2: Verify OSPFv3

Verify that the OSPFv3 configuration in Step 1 is working correctly. On R2, verify the OSPFv3 neighbor and OSPFv3 route.

R2#show ipv6 ospf neighbor 

Neighbor ID     Pri   State           Dead Time   Interface ID    Interface
1.1.1.1           1   FULL/DR         00:00:39    4               Ethernet0/0
3.3.3.3           1   FULL/BDR        00:00:30    4               Ethernet0/1
R2#show ipv6 route ospf
IPv6 Routing Table - 10 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
       U - Per-user Static route
       I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
       O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
O   2000:12:12:12::/64 [110/10]
     via ::, Ethernet0/0
O   2001:3:3:1::/64 [110/11]
     via FE80::3, Ethernet0/1
O   2001:3:3:2::/64 [110/11]
     via FE80::3, Ethernet0/1
O   2001:3:3:3::/64 [110/11]
     via FE80::3, Ethernet0/1

Step3: Change OSPFv3 cost

Change the cost of each Loopback interface on R3 so that OSPFv3 routes appear to be a configuration condition on R2. The cost of E0/1 on R2 is 10. To make the cost of the OSPF route in the configuration conditions, configure the OSPF cost as follows

Loopback0 2001:3:3:1::/64 cost 10
Loopback1 2001:3:3:2::/64 cost 20
Loopback2 2001:3:3:3::/64 cost 30

interface Loopback0
 ipv6 ospf cost 10
!
interface Loopback1
 ipv6 ospf cost 20
!
interface Loopback2
 ipv6 ospf cost 30

Step4: Verify OSPFv3 cost

Verify OSPFv3 routes on R2.

R2#show ipv6 route ospf
IPv6 Routing Table - 10 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
       U - Per-user Static route
       I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
       O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
O   2000:12:12:12::/64 [110/10]
     via ::, Ethernet0/0
O   2001:3:3:1::/64 [110/20]
     via FE80::3, Ethernet0/1
O   2001:3:3:2::/64 [110/30]
     via FE80::3, Ethernet0/1
O   2001:3:3:3::/64 [110/40]
     via FE80::3, Ethernet0/1

You can see that the cost of the OSPFv3 route is displayed in the same way as the configuration condition.

Step5: Configure route summary

To make OSPFv3 routes appear to be a configuration condition in the routing table on R1, summarize 2001:3:3:1::/64, 2001:3:3:2::/64, and 2001:3:3::/64 into 2001:3:3::/48. Route summarization in OSPFv3 is performed by ABR, so summary route is generated on R2.

ipv6 router ospf 1
 area 1 range 2001:3:3::/48

Step6: Verify route summary

Verify the route summary configuration. On R2, which generates summary route, use the show ipv6 opsf command. Also, there is an LSA type 3 that represents summary route in the LSDB of area 0.

R2#show ipv6 ospf 
 Routing Process "ospfv3 1" with ID 2.2.2.2
-- omitted --
 Number of areas in this router is 2. 2 normal 0 stub 0 nssa
 Reference bandwidth unit is 100 mbps
    Area BACKBONE(0)
        Number of interfaces in this area is 1
        SPF algorithm executed 4 times
        Number of LSA 8. Checksum Sum 0x0387AA
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0
    Area 1
        Number of interfaces in this area is 1
        SPF algorithm executed 4 times
        Area ranges are
          2001:3:3::/48 Active(40) Advertise 
        Number of LSA 9. Checksum Sum 0x031954
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0
R2#show ipv6 ospf database inter-area prefix 

            OSPFv3 Router with ID (2.2.2.2) (Process ID 1)

                Inter Area Prefix Link States (Area 0)

-- omitted --

  LS age: 718
  LS Type: Inter Area Prefix Links
  Link State ID: 5
  Advertising Router: 2.2.2.2
  LS Seq Number: 80000001
  Checksum: 0x5357
  Length: 36
  Metric: 40 
  Prefix Address: 2001:3:3::
  Prefix Length: 48, Options: None


                Inter Area Prefix Link States (Area 1)

-- omitted --

The metric of summary route is the maximum metric of detailed routes contained within the scope of the summary route. The maximum metric for a detailed route contained within the scope of summary route is 40 for 2001:3:3:3::/64. Therefore, the metric of the summary route is 40.

Note that the default metric for summary routes is different from that for OSPFv2. In OSPFv2, the metric of summary route is the minimum metric of detailed routes contained within the scope of the summary route.

Please also refer to the following article about an example of configuring an OSPFv2 route summary.

N-Study

Cisco OSPF Route Summary Configuration Example | N-Study

https://www.n-study.com/en/ospf-detail/cisco-ospf-route-summary-configuration-example/

This is an example of configuring OSPF inter-area route summary on a Cisco router. Notice the default cost of the default summary route.

And in the routing table on R1, the summary route of 2001:3:3::/48 is seen with metric 50, just like the configuration condition.

R1#show ipv6 route ospf
IPv6 Routing Table - 7 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
       U - Per-user Static route
       I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
       O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
OI  2001:3:3::/48 [110/50]
     via FE80::2, Ethernet0/0
O   2001:12:12:12::/64 [110/10]
     via ::, Ethernet0/0
OI  2001:23:23:23::/64 [110/20]
     via FE80::2, Ethernet0/0