Configuring OSPF
OSPF Configuration Examples

IPC-244

Cisco IOS IP Configuration Guide
U - per-user static route, o - ODR
Gateway of last resort is not set
C 1.0.0.0/8 is directly connected, Loopback0
10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O 10.0.1.3/32 [110/100] via 10.0.1.3, 00:39:08, Serial0
C 10.0.1.0/24 is directly connected, Serial0
O 10.0.1.5/32 [110/5] via 10.0.1.5, 00:39:08, Serial0
O 10.0.1.4/32 [110/10] via 10.0.1.4, 00:39:08, Serial0
OSPF Point-to-Multipoint, Nonbroadcast Example

The following example illustrates a point-to-multipoint network with nonbroadcast:

interface Serial0
ip address 10.0.1.1 255.255.255.0
ip ospf network point-to-multipoint non-broadcast
encapsulation frame-relay
no keepalive
frame-relay local-dlci 200
frame-relay map ip 10.0.1.3 202
frame-relay map ip 10.0.1.4 203
frame-relay map ip 10.0.1.5 204
no shut
!
router ospf 1
network 10.0.1.0 0.0.0.255 area 0
neighbor 10.0.1.3 cost 5
neighbor 10.0.1.4 cost 10
neighbor 10.0.1.5 cost 15

The following example is the configuration for the router on the other side:

interface Serial9/2
ip address 10.0.1.3 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-multipoint non-broadcast
no ip mroute-cache
no keepalive
no fair-queue
frame-relay local-dlci 301
frame-relay map ip 10.0.1.1 300
no shut
!
router ospf 1
network 10.0.1.0 0.0.0.255 area 0

The output shown for neighbors in the first configuration is as follows:

Router# show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
4.1.1.1 1 FULL/ - 00:01:52 10.0.1.5 Serial0
3.1.1.1 1 FULL/ - 00:01:52 10.0.1.4 Serial0
2.1.1.1 1 FULL/ - 00:01:52 10.0.1.3 Serial0
Variable-Length Subnet Masks Example

OSPF, static routes, and IS-IS support variable-length subnet masks (VLSMs). With VLSMs, you can

use different masks for the same network number on different interfaces, which allows you to conserve

IP addresses and more efficiently use available address space.