IP OSPF Network Broadcast Command on CISCO Router/Switch

Command

IP OSPF Network Broadcast

Use

This command manually sets the OSPF network type to broadcast, this is a default for ethernet links.
The Broadcast network type has a DR election.

Syntax

Router(config-if)#ip ospf network broadcast

Example

In this example, we will configure R4’s frame-relay link to use the broadcast network type

First we’ll configure OSPF on R1, R3, and R4 for all interfaces.

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

After a couple minutes R4 still doesn’t have any adjacencies

R4(config-router)#do show ip ospf neighbor

R4(config-router)#

Notice that the OSPF network type is non_broadcast so it will require unicast updates.

R4(config)#do show ip ospf interface s0/0
Serial0/0 is up, line protocol is up
Internet Address 10.4.4.4/24, Area 0
Process ID 1, Router ID 4.5.5.5, Network Type NON_BROADCAST, Cost: 64
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 4.5.5.5, Interface address 10.4.4.4
No backup designated router on this network
Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
oob-resync timeout 120
Hello due in 00:00:25
Supports Link-local Signaling (LLS)
Index 1/1, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 0, maximum is 0
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)

After we configure the broadcast network type on all routers, the adjacencies form.

R4(config)#int s0/0
R4(config-if)#ip ospf network broadcast

R4(config-if)#
*Mar 1 01:02:07.627: %OSPF-5-ADJCHG: Process 1, Nbr 111.111.111.111 on Serial0/0 from LOADING to FULL, Loading Done
R4(config-if)#
*Mar 1 01:02:11.707: %OSPF-5-ADJCHG: Process 1, Nbr 133.133.133.133 on Serial0/0 from LOADING to FULL, Loading Done
R4(config-if)#do show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface
111.111.111.111 1 FULL/DROTHER 00:00:30 10.4.4.1 Serial0/0
133.133.133.133 1 FULL/DR 00:00:30 10.4.4.3 Serial0/0
R4(config-if)#

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