Virtual Links
Virtual links are used to connect a temporarily-disjointed non-backbone area to the backbone area, or to repair a non-contiguous backbone area. In this example, the ABR R3 has temporarily lost connection to Area 0, in turn disconnecting Area 2 from the backbone area. The virtual link between ABR R1 and ABR R2 connects Area 2 to Area 0. Area 1 is used as a transit area.
Topology
Figure 12-91: OSPFv3 Virtual Links
Configuration
R1
#configure terminal | Enter configure mode. |
(config)#interface lo | Setup loopback interface |
(config-if)#ip address 1.1.1.1/32 secondary | Specify loopback interface address |
(config)#interface eth1 | Enter interface mode. |
(config-if)#ipv6 router ospf area 0 | Enable OSPFv3 routing on this interface, and assign the Area ID (0). |
(config-if)#exit | Exit interface mode. |
(config)#interface eth2 | Enter interface mode. |
(config-if)#ipv6 router ospf area 1 | Enable OSPFv3 routing on this interface, and assign the Area ID (1). |
(config-if)#exit | Exit interface mode. |
(config)#router ipv6 ospf | Create an OSPFv3 routing instance. |
(config-router)#router-id 1.1.1.1 | Specify a Router ID (1.1.1.1) for the OSPFv3 routing process. |
(config-router)#area 1 virtual-link 2.2.2.2 | Configure a virtual link between this router R1 and R2 (Router ID 2.2.2.2) through transit area 1. |
(config-router)#commit | Commit the candidate configuration to the running configuration. |
R2
#configure terminal | Enter configure mode. |
(config)#interface lo | Setup loopback interface |
(config-if)#ip address 2.2.2.2/32 secondary | Specify loopback interface address |
(config)#interface eth1 | Enter interface mode. |
(config-if)#ipv6 router ospf area 1 | Enable OSPFv3 routing on this interface, and assign the Area ID (1). |
(config-if)#exit | Exit interface mode. |
(config)#interface eth2 | Enter interface mode. |
(config-if)#ipv6 router ospf area 2 | Enable OSPFv3 routing on this interface, and assign the Area ID (2). |
(config-if)#exit | Exit interface mode. |
(config)#router ipv6 ospf | Create an OSPFv3 routing instance. |
(config-router)#router-id 2.2.2.2 | Specify a Router ID (2.2.2.2) for the OSPFv3 routing process. |
(config-router)#area 1 virtual-link 1.1.1.1 | Configure a virtual link between this router R1 and R2 (Router ID 1.1.1.1) through transit area 1. |
(config-router)#commit | Commit the candidate configuration to the running configuration. |
R4
#configure terminal | Enter configure mode. |
(config)#interface eth1 | Enter interface mode. |
(config-if)#ipv6 router ospf area 1 | Enable OSPFv3 routing on this interface, and assign the Area ID (1). |
(config-if)#exit | Exit interface mode. |
(config)#interface eth2 | Enter interface mode. |
(config-if)#ipv6 router ospf area 1 | Enable OSPFv3 routing on this interface, and assign the Area ID (1). |
(config-if)#exit | Exit interface mode. |
(config)#router ipv6 ospf | Create an OSPFv3 routing instance. |
(config-router)#router-id 4.4.4.4 | Specify a Router ID (4.4.4.4) for the OSPFv3 routing process. |
(config-router)#commit | Commit the candidate configuration to the running configuration. |
R5
#configure terminal | Enter configure mode. |
(config)#interface eth2 | Enter interface mode. |
(config-if)#ipv6 router ospf area 2 | Enable OSPFv3 routing on this interface, and assign the Area ID (2). |
(config-if)#exit | Exit interface mode. |
(config)#router ipv6 ospf | Create an OSPFv3 routing instance. |
(config-router)#router-id 5.5.5.5 | Specify a Router ID (5.5.5.5) for the OSPFv3 routing process. |
(config-router)#commit | Commit the candidate configuration to the running configuration. |
R6
#configure terminal | Enter configure mode. |
(config)#interface eth1 | Enter interface mode. |
(config-if)#ipv6 router ospf area 0 | Enable OSPFv3 routing on this interface, and assign the Area ID (0). |
(config-if)#exit | Exit interface mode. |
(config)#router ipv6 ospf | Create an OSPFv3 routing instance. |
(config-router)#router-id 6.6.6.6 | Specify a Router ID (6.6.6.6) for the OSPFv3 routing process. |
(config-router)#commit | Commit the candidate configuration to the running configuration. |
Validation
R2
#show ipv6 ospf n
OSPFv3 Process (*null*)
Neighbor ID Pri State Dead Time Interface Instance ID
10.10.10.10 1 Full/DR 00:00:31 eth1 0
3.3.3.3 1 Full/DR 00:00:32 eth2 0
2.2.2.2 1 Full/ - inactive VLINK2147479553 0
#show ipv6 ospf virtual-links
Virtual Link VLINK2147479553 to router 2.2.2.2 is up
Transit area 0.0.0.1 via interface eth2, instance ID 0
Hello suppression Enabled
DoNotAge LSA allowed
Local address 2ffe::11/128
Remote address 3ffe::11/128
Transmit Delay is 1 sec, State Point-To-Point,
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in inactive
Adajcency state Full
# show ipv6 ospf
Routing Process "OSPFv3 (*null*)" with ID 1.1.1.1
Process uptime is 5 minutes
This router is an ABR, ABR Type is Alternative Cisco (RFC3509)
This router is an ASBR (injecting external routing information)
SPF schedule delay initial 0.500 secs
SPF schedule delay min 0.500 secs
SPF schedule delay max 50.0 secs
Minimum LSA interval 5 secs, Minimum LSA arrival 1 secs
Number of incoming current DD exchange neighbors 0/5
Number of outgoing current DD exchange neighbors 0/5
Number of external LSA 0. Checksum Sum 0x0000
Number of AS-Scoped Unknown LSA 0
Number of LSA originated 17
Number of LSA received 50
Number of areas in this router is 2
Area BACKBONE(0)
Number of interfaces in this area is 2(2)
SPF algorithm executed 8 times
Number of LSA 23. Checksum Sum 0xB35D8
Number of Unknown LSA 0
Area 0.0.0.1
Number of interfaces in this area is 1(1)
SPF algorithm executed 13 times
Number of LSA 16. Checksum Sum 0x7845A
Number of Unknown LSA 0
Dste Staus: Disabled
#show ipv6 ospf route
OSPFv3 Process (*null*)
Codes: C - connected, D - Discard, 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
Destination Metric
Next-hop
C 1ffe::/64 1
directly connected, eth1, Area 0.0.0.0
C 2ffe::/64 1
directly connected, eth2, TransitArea 0.0.0.1
C 2ffe::11/128 0
directly connected, eth2, TransitArea 0.0.0.1
O 3ffe::/64 1
directly connected, eth2, TransitArea 0.0.0.1
O 3ffe::11/128 2
via fe80::5054:ff:fe6f:334d, eth2, TransitArea 0.0.0.1
IA 4ffe::/64 3
via fe80::5054:ff:fe6f:334d, eth2, TransitArea 0.0.0.1
#
R3
#show ipv6 ospf n
OSPFv3 Process (*null*)
Neighbor ID Pri State Dead Time Interface Instance ID
1.1.1.1 1 Full/Backup 00:00:35 eth1 0
2.2.2.2 1 Full/Backup 00:00:30 eth2 0
# show ipv6 ospf
Routing Process "OSPFv3 (*null*)" with ID 3.3.3.3
Process uptime is 5 minutes
This router is an ASBR (injecting external routing information)
SPF schedule delay initial 0.500 secs
SPF schedule delay min 0.500 secs
SPF schedule delay max 50.0 secs
Minimum LSA interval 5 secs, Minimum LSA arrival 1 secs
Number of incoming current DD exchange neighbors 0/5
Number of outgoing current DD exchange neighbors 0/5
Number of external LSA 0. Checksum Sum 0x0000
Number of AS-Scoped Unknown LSA 0
Number of LSA originated 10
Number of LSA received 23
Number of areas in this router is 1
Area 0.0.0.1
Number of interfaces in this area is 2(2)
SPF algorithm executed 14 times
Number of LSA 16. Checksum Sum 0x7845A
Number of Unknown LSA 0
Dste Staus: Disabled
#show ipv6 ospf route
OSPFv3 Process (*null*)
Codes: C - connected, D - Discard, 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
Destination Metric
Next-hop
IA 1ffe::/64 2
via fe80::5054:ff:feb7:cc69, eth1, TransitArea 0.0.0.1
C 2ffe::/64 1
directly connected, eth2, TransitArea 0.0.0.1
O 2ffe::11/128 1
via fe80::5054:ff:feb7:cc69, eth1, TransitArea 0.0.0.1
C 3ffe::/64 1
directly connected, eth1, TransitArea 0.0.0.1
O 3ffe::11/128 1
via fe80::5054:ff:fec5:2430, eth2, TransitArea 0.0.0.1
IA 4ffe::/64 2
via fe80::5054:ff:fec5:2430, eth2, TransitArea 0.0.0.1
R4
#show ipv6 ospf n
OSPFv3 Process (*null*)
Neighbor ID Pri State Dead Time Interface Instance ID
3.3.3.3 1 Full/DR 00:00:31 eth1 0
1.1.1.1 1 Full/ - inactive VLINK2147479554 0
#show ipv6 ospf virtual-links
Virtual Link VLINK2147479554 to router 1.1.1.1 is up
Transit area 0.0.0.1 via interface eth1, instance ID 0
Hello suppression Enabled
DoNotAge LSA allowed
Local address 3ffe::11/128
Remote address 2ffe::11/128
Transmit Delay is 1 sec, State Point-To-Point,
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in inactive
Adajcency state Full
# show ipv6 ospf
Routing Process "OSPFv3 (*null*)" with ID 2.2.2.2
Process uptime is 4 minutes
This router is an ABR, ABR Type is Alternative Cisco (RFC3509)
This router is an ASBR (injecting external routing information)
SPF schedule delay initial 0.500 secs
SPF schedule delay min 0.500 secs
SPF schedule delay max 50.0 secs
Minimum LSA interval 5 secs, Minimum LSA arrival 1 secs
Number of incoming current DD exchange neighbors 0/5
Number of outgoing current DD exchange neighbors 0/5
Number of external LSA 0. Checksum Sum 0x0000
Number of AS-Scoped Unknown LSA 0
Number of LSA originated 26
Number of LSA received 37
Number of areas in this router is 3
Area BACKBONE(0)
Number of interfaces in this area is 1(1)
SPF algorithm executed 3 times
Number of LSA 23. Checksum Sum 0xB35D8
Number of Unknown LSA 0
Area 0.0.0.1
Number of interfaces in this area is 1(1)
SPF algorithm executed 11 times
Number of LSA 16. Checksum Sum 0x7845A
Number of Unknown LSA 0
Area 0.0.0.2
Number of interfaces in this area is 1(1)
SPF algorithm executed 4 times
Number of LSA 11. Checksum Sum 0x5D8B7
Number of Unknown LSA 0
Dste Staus: Disabled
#show ipv6 ospf route
OSPFv3 Process (*null*)
Codes: C - connected, D - Discard, 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
Destination Metric
Next-hop
O 1ffe::/64 3
via fe80::5054:ff:fe1d:eace, eth1, TransitArea 0.0.0.1
O 2ffe::/64 1
directly connected, eth1, TransitArea 0.0.0.1
O 2ffe::11/128 2
via fe80::5054:ff:fe1d:eace, eth1, TransitArea 0.0.0.1
C 3ffe::/64 1
directly connected, eth1, TransitArea 0.0.0.1
C 3ffe::11/128 0
directly connected, eth1, TransitArea 0.0.0.1
C 4ffe::/64 1
directly connected, eth2, Area 0.0.0.2
Last modified date: 10/16/2023