Enable OSPF on an Interface
The diagram shows the minimum configuration required to enable OSPF on an interface. R1 and R2 are two routers in Area 0 connecting to network 10.10.10.0/24.
Note: Configure one interface so that it belongs to only one area. It is possible, however, to configure different interfaces on a router to belong to different areas.
Topology
Figure 4-9: Basic OSPF Topology
R1
#configure terminal | Enter configure mode |
(config)#router ospf 100 | Configure the routing process, and specify the Process ID (100). The Process ID should be a unique positive integer identifying the routing process. |
(config-router)#network 10.10.10.0/24 area 0 | Define the interface (10.10.10.0/24) on which OSPF runs, and associate the area ID (0) with the interface (area ID 0 specifies the backbone area). |
R2
#configure terminal | Enter configure mode |
(config)#router ospf 200 | Configure the routing process, and specify the Process ID (200). The Process ID should be a unique positive integer identifying the routing process. |
(config-router)#network 10.10.10.0/24 area 0 | Define the interface (10.10.10.0/24) on which OSPF runs, and associate the area ID (0) with the interface. |
Validation
R1
#show ip ospf
Routing Process "ospf 100" with ID 10.12.26.88
Process uptime is 1 minute
Process bound to VRF default
Conforms to RFC2328, and RFC1583 Compatibility flag is disabled
Supports only single TOS(TOS0) routes
Supports opaque LSA
Supports Graceful Restart
SPF schedule delay initial 0 secs 500 msecs
SPF schedule delay min 0 secs 500 msecs
SPF schedule delay max 50 secs 0 msecs
Refresh timer 10 secs
Number of incomming current DD exchange neighbors 0/64
Number of outgoing current DD exchange neighbors 0/64
Initial LSA throttle delay 0 secs 0 msecs
Minimum hold time for LSA throttle 5 secs 0 msecs
Maximum wait time for LSA throttle 5 secs 0 msecs
Minimum LSA arrival 1 secs 0 msecs
Number of external LSA 0. Checksum 0x000000
Number of opaque AS LSA 0. Checksum 0x000000
Number of non-default external LSA 0
External LSA database is unlimited.
Number of LSA originated 4
Number of LSA received 4
Number of areas attached to this router: 1
Area 0.0.0.0 (BACKBONE)
Number of interfaces in this area is 1(1)
Number of fully adjacent neighbors in this area is 1
Area has no authentication
SPF algorithm last executed 00:00:08.102 ago
SPF algorithm executed 3 times
Number of LSA 7. Checksum 0x0312b5
Dste Staus: Disabled
#show ip ospf interface
eth2 is up, line protocol is up
Internet Address 10.10.10.10/24, Area 0.0.0.0, MTU 1500
Process ID 100, VRF (default), Router ID 10.12.26.88, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DR, Priority 1, TE Metric 1
Designated Router (ID) 10.12.26.88, Interface Address 10.10.10.10
Backup Designated Router (ID) 10.12.26.89, Interface Address 10.10.10.11
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:11
Neighbor Count is 1, Adjacent neighbor count is 1
Suppress hello for 0 neighbor(s)
Hello received 13 sent 19, DD received 3 sent 4
LS-Req received 1 sent 1, LS-Upd received 3 sent 5
LS-Ack received 3 sent 3, Discarded 0
No authentication
#show ip ospf neighbor
Total number of full neighbors: 1
OSPF process 100 VRF(default):
Neighbor ID Pri State Dead Time Address Interface Instance ID
10.12.26.89 1 Full/Backup 00:00:39 10.10.10.11 eth2 0
#show ip ospf route
OSPF process 100:
Codes: C - connected, D - Discard, 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
C 10.10.10.0/24 [1] is directly connected, eth2, Area 0.0.0.0
R2
#show ip ospf
Routing Process "ospf 200" with ID 10.12.26.89
Process uptime is 1 minute
Process bound to VRF default
Conforms to RFC2328, and RFC1583 Compatibility flag is disabled
Supports only single TOS(TOS0) routes
Supports opaque LSA
Supports Graceful Restart
SPF schedule delay initial 0 secs 500 msecs
SPF schedule delay min 0 secs 500 msecs
SPF schedule delay max 50 secs 0 msecs
Refresh timer 10 secs
Number of incomming current DD exchange neighbors 0/64
Number of outgoing current DD exchange neighbors 0/64
Initial LSA throttle delay 0 secs 0 msecs
Minimum hold time for LSA throttle 5 secs 0 msecs
Maximum wait time for LSA throttle 5 secs 0 msecs
Minimum LSA arrival 1 secs 0 msecs
Number of external LSA 0. Checksum 0x000000
Number of opaque AS LSA 0. Checksum 0x000000
Number of non-default external LSA 0
External LSA database is unlimited.
Number of LSA originated 3
Number of LSA received 5
Number of areas attached to this router: 1
Area 0.0.0.0 (BACKBONE)
Number of interfaces in this area is 1(1)
Number of fully adjacent neighbors in this area is 1
Area has no authentication
SPF algorithm last executed 00:00:45.638 ago
SPF algorithm executed 4 times
Number of LSA 7. Checksum 0x0312b5
Dste Staus: Disabled
#show ip ospf interface
eth1 is up, line protocol is up
Internet Address 10.10.10.11/24, Area 0.0.0.0, MTU 1500
Process ID 200, VRF (default), Router ID 10.12.26.89, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State Backup, Priority 1, TE Metric 1
Designated Router (ID) 10.12.26.88, Interface Address 10.10.10.10
Backup Designated Router (ID) 10.12.26.89, Interface Address 10.10.10.11
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:06
Neighbor Count is 1, Adjacent neighbor count is 1
Suppress hello for 0 neighbor(s)
Hello received 30 sent 31, DD received 4 sent 3
LS-Req received 1 sent 1, LS-Upd received 5 sent 3
LS-Ack received 2 sent 3, Discarded 0
No authentication
#show ip ospf neighbor
Total number of full neighbors: 1
OSPF process 200 VRF(default):
Neighbor ID Pri State Dead Time Address Interface Instance ID
10.12.26.88 1 Full/DR 00:00:33 10.10.10.10 eth1 0
#show ip ospf route
OSPF process 200:
Codes: C - connected, D - Discard, 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
C 10.10.10.0/24 [1] is directly connected, eth1, Area 0.0.0.0
Last modified date: 07-13-2023