WB1 6.2 OSPF over Non-Broadcast Media

As seen in the show ip ospf interface output the default network type for a multipoint Frame Relay
interface is NON_BROADCAST.

要確認的是Hub(R5)必須要是DR，這樣才有辦法更新路由給所有的Spoke(R1~R4)

Rack1R5#show ip ospf neighbor
Neighbor ID     Pri   State           Dead Time   Address         Interface
150.1.1.1         0   FULL/DROTHER    00:01:44    155.1.0.1       Serial0/0
150.1.2.2         0   FULL/DROTHER    00:01:58    155.1.0.2       Serial0/0
150.1.3.3         0   FULL/DROTHER    00:01:38    155.1.0.3       Serial0/0
223.255.255.255   0   FULL/DROTHER    00:01:49    155.1.0.4       Serial0/0
150.1.8.8         1   FULL/DR         00:00:31    155.1.58.8      FastEthernet0/0
Rack1R5#

我是直接在R5上，給 priority 255 (DR)

Rack1R5#sh run interface serial 0/0
Building configuration...
Current configuration : 314 bytes
!
interface Serial0/0
 ip address 155.1.0.5 255.255.255.0
 encapsulation frame-relay
 ip ospf priority 255
 ip ospf 1 area 0
 clock rate 2000000
 frame-relay map ip 155.1.0.4 504
 frame-relay map ip 155.1.0.3 503
 frame-relay map ip 155.1.0.2 502
 frame-relay map ip 155.1.0.1 501
 no frame-relay inverse-arp
end
Rack1R5#

直接在R1~R4上，給 priority 0 (DROTHER)

Rack1R1#sh run interface ser0/0
Building configuration...
Current configuration : 312 bytes
!
interface Serial0/0
 ip address 155.1.0.1 255.255.255.0
 encapsulation frame-relay
 ip ospf priority 0
 ip ospf 1 area 0
 clock rate 2000000
 frame-relay map ip 155.1.0.4 105
 frame-relay map ip 155.1.0.3 105
 frame-relay map ip 155.1.0.2 105
 frame-relay map ip 155.1.0.5 105
 no frame-relay inverse-arp
end
Rack1R1#


每一台Spoke上所學到的路由都是原本的路由器所產生的，要注意...frame-relay map


Rack1R2#show ip route ospf
     51.0.0.0/32 is subnetted, 1 subnets
O E2    51.51.51.51 [110/20] via 192.10.1.254, 00:25:01, FastEthernet0/0
     155.1.0.0/24 is subnetted, 13 subnets
O IA    155.1.146.0 [110/65] via 155.1.0.4, 00:23:27, Serial0/0
                    [110/65] via 155.1.0.1, 00:23:27, Serial0/0
O IA    155.1.10.0 [110/67] via 155.1.0.5, 00:23:27, Serial0/0
O IA    155.1.8.0 [110/66] via 155.1.0.5, 00:23:27, Serial0/0
O IA    155.1.9.0 [110/67] via 155.1.0.3, 00:23:27, Serial0/0
O IA    155.1.7.0 [110/66] via 155.1.0.3, 00:23:27, Serial0/0
O IA    155.1.5.0 [110/65] via 155.1.0.5, 00:23:27, Serial0/0
O IA    155.1.58.0 [110/65] via 155.1.0.5, 00:23:27, Serial0/0
O IA    155.1.37.0 [110/65] via 155.1.0.3, 00:23:27, Serial0/0
O IA    155.1.79.0 [110/66] via 155.1.0.3, 00:23:27, Serial0/0
O IA    155.1.67.0 [110/66] via 155.1.0.3, 00:23:27, Serial0/0
O IA    155.1.108.0 [110/66] via 155.1.0.5, 00:23:27, Serial0/0
     150.1.0.0/16 is variably subnetted, 2 subnets, 2 masks
O IA    150.1.7.7/32 [110/66] via 155.1.0.3, 00:23:28, Serial0/0

Rack1R2#show ip route 155.1.10.10
Routing entry for 155.1.10.0/24
  Known via "ospf 1", distance 110, metric 67, type inter area
  Last update from 155.1.0.5 on Serial0/0, 00:23:56 ago
  Routing Descriptor Blocks:
  * 155.1.0.5, from 150.1.5.5, 00:23:56 ago, via Serial0/0
      Route metric is 67, traffic share count is 1
 
Rack1R2#show ip route 155.1.0.5
Routing entry for 155.1.0.0/24
  Known via "connected", distance 0, metric 0 (connected, via interface)
  Routing Descriptor Blocks:
  * directly connected, via Serial0/0
      Route metric is 0, traffic share count is 1

Rack1R2#show frame-relay map | include 155.1.0.5
Serial0/0 (up): ip 155.1.0.5 dlci 205(0xCD,0x30D0), static,

Rack1R2#ping 155.1.10.10
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 155.1.10.10, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 28/43/60 ms
Rack1R2#

There are basically two ways to solve this design problem, either change the next-hop to something the router does know how to resolve, or allow the router to properly resolve the current next-hop. In this solution, the current next-hop is resolved by adding additional frame-relay map statements. Changing the next-hop value is explored in the next few examples with the point-to-multipoint
OSPF network type.