2-19 area transit-area-id virtual-link router-id hi-interval seconds

2-19 area transit-area-id virtual-link router-id hello-interval seconds

Syntax Description:

• transit-area-id ” The OSPF area ID of the area connecting the two ABRs that the virtual link will cross. This value can be entered as a decimal number in the range of 0 to 4,294,967,295 or in IP address form in the range 0.0.0.0 to 255.255.255.255. The transit area cannot be a stub area.

• router-id ” OSPF router ID of the router at the remote end of the virtual link.

• seconds ” The time in seconds between sending Hello packets over the virtual link. The range of values is 1 “8192 seconds. The default value is 10 seconds (30 seconds on a nonbroadcast multiaccess [NBMA] network).

Purpose: OSPF Hello packets are used to initially establish the neighbor relationship. Once the neighbor relationship is established, the packets are used as a keepalive mechanism to determine if the neighbor at the other end of the virtual link is still active. The Hello interval should be less than the dead interval (see Command 2-18).

Initial Cisco IOS Software Release: 10.0

Configuration Example: Modifying the Hello Interval Over a Virtual Link

Configure the network in Figure 2-19 to observe the default timer values over the virtual link. You will then experiment with adjusting the values of the Hello interval.

Figure 2-19. The Hello Interval Must Be Configured with the Same Value at Both Ends of an OSPF Virtual Link

 Router A  interface Loopback0   ip address 1.1.1.1 255.255.255.255   !   interface Serial0/1   ip address 10.1.1.1 255.255.255.252   clockrate 64000   !   router ospf 1   network 10.1.1.0 0.0.0.3 area 0   network 1.1.1.1 0.0.0.0 area 0  _______________________________________________________________________ Router B  interface Loopback0   ip address 2.2.2.2 255.255.255.255   !   interface Serial0   ip address 10.1.1.2 255.255.255.252   !   interface Serial1   ip address 10.1.1.5 255.255.255.252   clockrate 64000   !   router ospf 1    area 1 virtual-link 3.3.3.3    network 10.1.1.0 0.0.0.3 area 0   network 2.2.2.2 0.0.0.0 area 0   network 10.1.1.4 0.0.0.3 area 1  _______________________________________________________________________ Router C  interface Loopback0   ip address 3.3.3.3 255.255.255.255   !   interface Serial0   ip address 10.1.1.6 255.255.255.252   !   router ospf 1    area 1 virtual-link 2.2.2.2    network 3.3.3.3 0.0.0.0 area 2   network 10.1.1.4 0.0.0.3 area 1  

Verify that the virtual link is active and that all OSPF routes are being exchanged.

 rtrB#  show ip ospf virtual-links   Virtual Link OSPF_VL0 to router 3.3.3.3 is up  Run as demand circuit   DoNotAge LSA allowed.   Transit area 1, via interface Serial1, Cost of using 64   Transmit Delay is 1 sec, State POINT_TO_POINT,  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5   Hello due in 00:00:03  Adjacency State FULL (Hello suppressed) _______________________________________________________________________ rtrC#  show ip ospf virtual-links   Virtual Link OSPF_VL7 to router 2.2.2.2 is up  Run as demand circuit   DoNotAge LSA allowed.   Transit area 1, via interface Serial0, Cost of using 64   Transmit Delay is 1 sec, State POINT_TO_POINT,  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5   Hello due in 00:00:06  Adjacency State FULL (Hello suppressed) rtrC#  show ip route  Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP        D - EIGRP, EX - EIGRP external, 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, E - EGP        i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default        U - per-user static route, o - ODR Gateway of last resort is not set      1.0.0.0/32 is subnetted, 1 subnets  O       1.1.1.1 [110/129] via 10.1.1.5, 00:02:25, Serial0  2.0.0.0/32 is subnetted, 1 subnets  O       2.2.2.2 [110/65] via 10.1.1.5, 00:02:26, Serial0  3.0.0.0/24 is subnetted, 1 subnets C       3.3.3.0 is directly connected, Loopback0      10.0.0.0/30 is subnetted, 2 subnets  O       10.1.1.0 [110/128] via 10.1.1.5, 00:02:26, Serial0  C       10.1.1.4 is directly connected, Serial0 

Notice that the default Hello interval is 10 seconds and the default dead interval is 40 seconds. Modify the configuration on Router B to change the Hello interval to 11 seconds while leaving the value for the Hello interval on Router C set to the default of 10 seconds.

 Router B  router ospf 1    area 1 virtual-link 3.3.3.3 hello-interval 11    network 2.2.2.2 0.0.0.0 area 0   network 10.1.1.0 0.0.0.3 area 0   network 10.1.1.4 0.0.0.3 area 1  

Is the virtual link still active?

 rtrB#  show ip ospf virtual-links  Virtual Link OSPF_VL0 to router 3.3.3.3 is up   Run as demand circuit   DoNotAge LSA allowed.   Transit area 1, via interface Serial1, Cost of using 64   Transmit Delay is 1 sec, State POINT_TO_POINT,   Timer intervals configured,  Hello 11  , Dead 40, Wait 40, Retransmit 5     Hello due in 00:00:07 

The virtual link is up. Now check to see if the OSPF routes are being exchanged.

 rtrB#  show ip route  Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP        D - EIGRP, EX - EIGRP external, 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, E - EGP        i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default        U - per-user static route, o - ODR Gateway of last resort is not set      1.0.0.0/32 is subnetted, 1 subnets O       1.1.1.1 [110/65] via 10.1.1.1, 00:07:49, Serial0      2.0.0.0/32 is subnetted, 1 subnets C       2.2.2.2 is directly connected, Loopback0      10.0.0.0/30 is subnetted, 2 subnets C       10.1.1.0 is directly connected, Serial0 C       10.1.1.4 is directly connected, Serial1 

Router B has learned the routes being advertised by Router A but not the routes advertised by Router C. Because the Hello interval time on Router B does not match the Hello interval on Router C, routes will not be exchanged over the virtual link. Modify the Hello interval time on Router C to match the Hello interval time on Router B.

 Router C  router ospf 1   router ospf 1    area 1 virtual-link 2.2.2.2 hello-interval 11    network 3.3.3.3 0.0.0.0 area 2   network 10.1.1.4 0.0.0.3 area 1  

Verification

Verify that the Hello interval on Router C matches the dead interval on Router B.

 rtrC#  show ip ospf virtual-links  Virtual Link OSPF_VL7 to router 2.2.2.2 is up   Run as demand circuit   DoNotAge LSA allowed.   Transit area 1, via interface Serial0, Cost of using 64   Transmit Delay is 1 sec, State POINT_TO_POINT,   Timer intervals configured,  Hello 11  , Dead 41, Wait 40, Retransmit 5     Hello due in 00:00:00     Adjacency State FULL (Hello suppressed) 

Verify that all OSPF routes are now being exchanged.

 rtrA#  show ip route  Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP        D - EIGRP, EX - EIGRP external, 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, E - EGP        i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default        U - per-user static route, o - ODR Gateway of last resort is not set      1.0.0.0/32 is subnetted, 1 subnets  C       1.1.1.1 is directly connected, Loopback0  2.0.0.0/32 is subnetted, 1 subnets  O       2.2.2.2 [110/65] via 10.1.1.2, 00:09:04, Serial0/1  3.0.0.0/32 is subnetted, 1 subnets  O IA    3.3.3.3 [110/129] via 10.1.1.2, 00:09:04, Serial0/1  10.0.0.0/30 is subnetted, 2 subnets C       10.1.1.0 is directly connected, Serial0/1 O IA    10.1.1.4 [110/128] via 10.1.1.2, 00:09:04, Serial0/1 rtrB#  show ip route  Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP        D - EIGRP, EX - EIGRP external, 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, E - EGP        i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default        U - per-user static route, o - ODR Gateway of last resort is not set      1.0.0.0/32 is subnetted, 1 subnets  O       1.1.1.1 [110/65] via 10.1.1.1, 00:10:19, Serial0  2.0.0.0/32 is subnetted, 1 subnets  C       2.2.2.2 is directly connected, Loopback0  3.0.0.0/32 is subnetted, 1 subnets  O IA    3.3.3.3 [110/65] via 10.1.1.6, 00:10:20, Serial1  10.0.0.0/30 is subnetted, 2 subnets C       10.1.1.0 is directly connected, Serial0 C       10.1.1.4 is directly connected, Serial1 _______________________________________________________________________ rtrC#  show ip route  Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP        D - EIGRP, EX - EIGRP external, 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, E - EGP        i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default        U - per-user static route, o - ODR Gateway of last resort is not set      1.0.0.0/32 is subnetted, 1 subnets  O       1.1.1.1 [110/129] via 10.1.1.5, 00:11:10, Serial0  2.0.0.0/32 is subnetted, 1 subnets  O       2.2.2.2 [110/65] via 10.1.1.5, 00:11:11, Serial0  3.0.0.0/24 is subnetted, 1 subnets  C       3.3.3.0 is directly connected, Loopback0  10.0.0.0/30 is subnetted, 2 subnets O       10.1.1.0 [110/128] via 10.1.1.5, 00:11:11, Serial0 C       10.1.1.4 is directly connected, Serial0 

Troubleshooting

Step 1. Verify that there is a neighbor relationship between the OSPF routers by using the show ip ospf neighbor command.

Step 2. Verify that the transit area ID used in the area virtual-link command is the proper area.

Step 3. Verify that the router IDs used in the area virtual-link are correct.

Step 4. Verify that the Hello interval is being used on both ends of the virtual link.