11-2 neighbor ip-address cost cost

11-2 neighbor ip-address cost cost

Syntax Description:

• ip-address ” IP address of the OSPF neighbor. If a secondary address is used on the interface, then the primary address must be used with this command.

• cost ” The cost to reach the OSPF neighbor. The range of values is 1 to 65535.

Purpose: To configure the cost of an OSPF neighbor on a point-to-multipoint network.

Initial Cisco IOS Software Release: 11.3

Configuration Example: Modifying the Cost of an OSPF Neighbor on a Point-to-Multipoint Interface

The cost to reach an OSPF neighbor is, by default, the bandwidth of the network connecting the two neighbors divided into 100,000,000. In Figure 11-5, the bandwidth of the Frame Relay link is 2048 kbps. Therefore, the OSPF cost of the Frame Relay interfaces is 48 (100,000,000/2,048,000). The cost option of the neighbor command can be used to change the cost to reach the neighbor. The interface command ip ospf cost (see Section 19-3) can also be used to change this cost. The neighbor cost command can only be used on point-to-multipoint interfaces. The listing that follows the figure shows the configurations of the Frame Relay switch and Routers A and B.

Figure 11-5. The Default Cost of an OSPF Interface Is 100,000,000/(Interface Bandwidth in bps). The neighbor cost Command Can Be Used to Modify the Interface Cost

 Frame Switch  hostname frame-relay   !   frame-relay switching   !   interface Serial1/0   no ip address   no ip directed-broadcast   encapsulation frame-relay   no ip mroute-cache   no fair-queue   clockrate 2015232   frame-relay lmi-type ansi   frame-relay intf-type dce   frame-relay route 101 interface Serial1/1 110   frame-relay route 102 interface Serial1/2 120   frame-relay route 103 interface Serial1/3 130   !   interface Serial1/1   no ip address   no ip directed-broadcast   encapsulation frame-relay   clockrate 2015232   frame-relay lmi-type ansi   frame-relay intf-type dce   frame-relay route 110 interface Serial1/0 101   frame-relay route 112 interface Serial1/2 121   frame-relay route 113 interface Serial1/3 131  ________________________________________________________________________ Router A  interface Loopback0   ip address 1.1.1.1 255.255.255.255   !   interface Serial0/0   bandwidth 2048   ip address 10.1.1.1 255.255.255.252   encapsulation frame-relay   ip ospf network point-to-multipoint   frame-relay map ip 10.1.1.2 101 broadcast   no frame-relay inverse-arp   frame-relay lmi-type ansi   !   router ospf 1   network 1.1.1.1 0.0.0.0 area 1   network 10.1.1.0 0.0.0.3 area 0  ________________________________________________________________ Router B  interface Loopback0   ip address 2.2.2.2 255.255.255.255   !   interface Serial0   bandwidth 2048   ip address 10.1.1.2 255.255.255.252   encapsulation frame-relay   ip ospf network point-to-multipoint   frame-relay map ip 10.1.1.1 110 broadcast   no frame-relay inverse-arp   frame-relay lmi-type ansi   !   router ospf 1   network 2.2.2.2 0.0.0.0 area 2   network 10.1.1.0 0.0.0.3 area 0  

The interface command ip ospf network point-to-multipoint (see Section 19-15) is used because the neighbor cost command will work only on a point-to-multipoint interface. Display the IP routing table on Router B to see the cost of reaching the loopback network on Router A.

 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 IA    1.1.1.1 [110/49] via 10.1.1.1, 00:22:11, Serial0  2.0.0.0/32 is subnetted, 1 subnets C       2.2.2.2 is directly connected, Loopback0      172.16.0.0/24 is subnetted, 1 subnets C       172.16.1.0 is directly connected, Ethernet0      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks C       10.1.1.0/30 is directly connected, Serial0 O       10.1.1.1/32 [110/10] via 10.1.1.1, 00:22:11, Serial0 

The cost is the sum of the cost of the loopback interface (1) and the cost of the Frame Relay link (48) for a total cost of 49. Modify the configuration on Router B to change the cost of the Frame Relay link to 10.

 Router B  router ospf 1   network 2.2.2.2 0.0.0.0 area 2   network 10.1.1.0 0.0.0.3 area 0    neighbor 10.1.1.1 cost 10   

Verification

Verify that the cost of the Frame Relay interface, as seen by Router B, has changed to 10.

 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 IA    1.1.1.1 [110/11] via 10.1.1.1, 00:01:49, Serial0  2.0.0.0/32 is subnetted, 1 subnets C       2.2.2.2 is directly connected, Loopback0      172.16.0.0/24 is subnetted, 1 subnets C       172.16.1.0 is directly connected, Ethernet0      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks C       10.1.1.0/30 is directly connected, Serial0 O       10.1.1.1/32 [110/10] via 10.1.1.1, 00:01:49, Serial0 

Troubleshooting

Step 1. Verify IP connectivity over the NBMA network by pinging the other end of the link. If the ping is unsuccessful , there is a problem with the interface configuration. Check the interface for the correct encapsulation, lmi-type, IP address, and DLCI mapping.

Step 2. Verify that the OSPF routers have established a FULL adjacency over the NBMA network.

Step 3. If the OSPF neighbors have a FULL adjacency, then the command neighbor cost should work. Remember that this command can be used only on a point-to-multipoint interface.