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Alright, we’ve finally made it to the last of the four-part series on configuring frame-relay. If you haven’t been following along, you may want to check out part one, part two, and part three before continuing.

In part four, we’ll continue on where we left off in part three. Our topology is shown here:

OSPF over frame-relay presents some unique challenges, depending on just how your frame-relay network is architected. Ours is pretty straightforward — we have a simple hub-and-spoke network (R1/R2/R3) as well as a point-to-point connection (R1/R4). We need full reachability between all of these routers, so it’s time to add in some OSPF.

NOTE: Arden Packeer, CCIE 20716 wrote up an excellent five-part series entitled “OSPF Network Types & Frame-Relay Series“. If you’re working with frame-relay and OSPF, I would highly recommend you read them. Because Arden did such a wonderful job (thanks!), I won’t bother repeating what he has already said.

In this article, we’re going to use both point-to-multipoint (R1/R2/R3) and point-to-point (R1/R4) to gain us full reachability throughout our routing domain. I’m a big fan of keeping things simple, and we can accomplish our goal with a minimum of effort.

On all routers, we’ll tell OSPF that we want all interfaces to participate in OSPF (in area 0). On R1, R2, and R3’s serial 0/0 interfaces, we’ll also need to specify that we’re using the point-to-multipoint network type. Let’s configure the routers, starting with R1:

R1# configure terminal
R1(config-router)# interface serial 0/0
R1(config-if)# ip ospf network point-to-multipoint
R1(config)# router ospf 1
R1(config-router)# network 0.0.0.0 255.255.255.255 area 0

R2# configure terminal
R2(config-router)# interface serial 0/0
R2(config-if)# ip ospf network point-to-multipoint
R2(config)# router ospf 1
R2(config-router)# network 0.0.0.0 255.255.255.255 area 0

R3# configure terminal
R3(config-router)# interface serial 0/0
R3(config-if)# ip ospf network point-to-multipoint
R3(config)# router ospf 1
R3(config-router)# network 0.0.0.0 255.255.255.255 area 0

After giving time for the adjacencies to come up, we can verify proper operation on R1:

R1(config-if)# do show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
172.16.123.3      0   FULL/  -        00:01:59    172.16.123.3    Serial0/0
172.16.123.2      0   FULL/  -        00:01:34    172.16.123.2    Serial0/0

Now, let’s configure OSPF on R4:

R4# configure terminal
R4(config)# router ospf 1
R4(config-router)# network 0.0.0.0 255.255.255.255 area 0

On R4, we should now see routes to all other devices and networks:

R4(config-router)# do show ip route | begin Gateway
Gateway of last resort is not set

     172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks
C       172.16.14.0/24 is directly connected, Serial0/0.14
O       172.16.123.3/32 [110/128] via 172.16.14.1, 00:00:42, Serial0/0.14
O       172.16.123.2/32 [110/128] via 172.16.14.1, 00:00:42, Serial0/0.14
O       172.16.123.1/32 [110/64] via 172.16.14.1, 00:00:42, Serial0/0.14

Let’s verify we have full reachability:

R4(config-router)# do ping 172.16.123.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.123.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/5/8 ms
R4(config-router)# do ping 172.16.123.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.123.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/8/12 ms
R4(config-router)# do ping 172.16.123.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.123.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/8/12 ms

Success!