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OSPFPrivileged EXEC

show ip ospf interface

Displays OSPF interface parameters and status, used to verify OSPF configuration and troubleshoot neighbor relationships.

Syntax·Privileged EXEC
show ip ospf interface

When to Use This Command

  • Verify that OSPF is enabled on the correct interfaces and that the network type is appropriate.
  • Check the OSPF cost, timer values, and neighbor state on a specific interface.
  • Troubleshoot OSPF adjacency issues by examining interface-specific OSPF settings.
  • Confirm the designated router (DR) and backup designated router (BDR) elections on multi-access networks.

Command Examples

Basic OSPF interface status on GigabitEthernet0/0

show ip ospf interface gigabitethernet 0/0
GigabitEthernet0/0 is up, line protocol is up
  Internet Address 192.168.1.1/24, Area 0
  Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router (ID) 1.1.1.1, Interface address 192.168.1.1
  Backup Designated router (ID) 2.2.2.2, Interface address 192.168.1.2
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:03
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 1, Adjacent neighbor count is 1
    Adjacent with neighbor 2.2.2.2  (Backup Designated Router)
  Suppress hello for 0 neighbor(s)

The interface is up and OSPF is active. The router is the DR (State DR) with priority 1. Hello timer is 10 seconds, dead timer 40 seconds. There is one adjacent neighbor (2.2.2.2) which is the BDR.

OSPF interface on a point-to-point serial link

show ip ospf interface serial 0/0/0
Serial0/0/0 is up, line protocol is up
  Internet Address 10.0.0.1/30, Area 0
  Process ID 1, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 64
  Transmit Delay is 1 sec, State POINT_TO_POINT
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:07
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 2/2, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 1, Adjacent neighbor count is 1
    Adjacent with neighbor 2.2.2.2
  Suppress hello for 0 neighbor(s)

This is a point-to-point link (Network Type POINT_TO_POINT). No DR/BDR election occurs. Cost is 64 (default for serial). One neighbor is fully adjacent.

Understanding the Output

The output shows OSPF parameters per interface. Key fields: 'Internet Address' and 'Area' confirm OSPF configuration. 'Process ID' and 'Router ID' identify the OSPF process. 'Network Type' (BROADCAST, POINT_TO_POINT, etc.) determines behavior. 'Cost' is used for SPF calculations. 'State' indicates the router's role (DR, BDR, DROTHER, or POINT_TO_POINT). 'Timer intervals' show Hello and Dead intervals; mismatched timers prevent adjacency. 'Neighbor Count' and 'Adjacent neighbor count' indicate how many neighbors are fully adjacent. 'Adjacent with neighbor' lists the neighbor router ID and role. Good values: interface up/up, state appropriate for network type, timers consistent, neighbor count >0. Bad values: interface down, state DOWN, mismatched timers, zero neighbors.

CCNA Exam Tips

1.

CCNA exam tip: On broadcast multi-access networks, the router with the highest OSPF priority becomes the DR; if priorities are equal, the highest router ID wins.

2.

CCNA exam tip: The 'show ip ospf interface' command is crucial for verifying OSPF network type and timer values, which must match between neighbors.

3.

CCNA exam tip: If the interface state is 'DOWN' or 'WAITING', check for mismatched OSPF parameters or Layer 1/2 issues.

4.

CCNA exam tip: On point-to-point links, there is no DR/BDR election; the state will be 'POINT_TO_POINT'.

Common Mistakes

Mistake 1: Assuming OSPF is enabled on an interface without verifying with 'show ip ospf interface' — the interface may be in the wrong area or passive.

Mistake 2: Forgetting that OSPF timers must match on both sides of a link; mismatched Hello/Dead timers prevent adjacency.

Mistake 3: Misinterpreting the 'State' field — on broadcast networks, a state of 'DROTHER' is normal for non-DR/BDR routers, not an error.

Related Commands

show ip ospf

Displays general information about OSPF routing process, including router ID, areas, and LSDB statistics, used to verify OSPF configuration and operational status.

show ip ospf neighbor

Displays OSPF neighbor information to verify adjacency formation and troubleshoot OSPF neighbor relationships.

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