Sunday, June 5, 2011

The 'show ip ospf interface' EXEC Command

Below shows the output of the show ip ospf interface [intf-type intf-num] command on RT1.
The output of the command varies upon the different type of interfaces.
RT1#sh ip ospf interface fa0/0
FastEthernet0/0 is up, line protocol is up
  Internet Address, Area 0
  Process ID 100, Router ID, Network Type BROADCAST, Cost: 1
  Transmit Delay is 1 sec, State BDR, Priority 1
  Designated Router (ID), Interface address
  Backup Designated router (ID), Interface address
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:05
  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  (Designated Router)
  Suppress hello for 0 neighbor(s)

Below describes the various information that is being revealed in the mentioned command:
Field Description
Interface State The 1st line of the output displays the Layer 1 and Layer 2 states of an interface. The interface should be in the up / up state.
IP Address and Area Indicates the IP address configured on an interface and the OSPF area in which the interface resides in.
Process ID Indicates the OSPF process to which the interface belongs. The OSPF Process ID is locally significant therefore 2 neighboring OSPF routers with different Process IDs can establish adjacency. An OSPF router can run multiple OSPF processes, and the Process IDs are being used to differentiate the OSPF processes.
Router ID The OSPF Router ID is selected upon the start of an OSPF process. Once the Router ID is elected, it does not change unless the OSPF process restarts upon issuing the clear ip ospf process command.
Network Type Indicates the network type (eg: BROADCAST, NON_BROADCAST, POINT_TO_MULTIPOINT, POINT_TO_POINT) of the interface. Routers with different network type interfaces are able to become neighbor and established FULL adjacency; however, inconsistency link-state information affects the operation of OSPF and prevents routes from being installed into the routing table.
Cost Indicates the OSPF metric associated with the interface. The ip ospf cost {cost} interface subcommand specifies the cost of an interface.
Transmit Delay Indicates the transmission and propagation delay of an interface. The LS Age of an LSA is incremented by this timer value in order to accommodate transmission and propagation delay of an interface. The transmit delay timer is important on low speed links where the transmission delay is significant. The default value is 1 second.
Priority Indicates the OSPF priority on the interface that is being used when electing the DR and BDR on a broadcast network media. The router with the highest priority becomes the DR. If the priorities are same, the router with the highest Router ID becomes the DR. The default value is 1. A router with a priority of 0 never participates in the DR/BDR election process and is known as a DROTHER.
Designated Router Indicates the Router ID of the DR on a broadcast network.
DR Interface Address Indicates the physical IP address of the DR that connects to the broadcast network.
Backup DR Indicates the Router ID of the BDR on a broadcast network.
BDR Interface Address Indicates the physical IP address of the BDR that connects to the broadcast network.
Timer Intervals Hello – Interval time in seconds for sending OSPF Hello packets.
Dead – Time in seconds to wait before declaring a neighbor is dead.
Wait – Time to wait (wait period) before electing the DR.
Retransmit – Time to wait before retransmit a LSA when it has not been acknowledged. This ensures reliable flooding.
OOB-Resync Timeout – Utilized by RFC4811 OSPF Out-of-Band LSDB Resynchronization to limit the amount of time allowed for 2 neighboring routers to resynchronize their LSDBs upon an OOB-Resync event.
Hello Due In – A Hello packet will be sent upon this timer elapsed.
Index Indicates the index of the interface flood lists for the area and autonomous system / OSPF routing domain. Indicated as area/as.
Flood Queue Length Indicates the number of LSAs waiting to be flooded out an interface.
Next Indicates the pointer to the flooding lists for next the LSAs to be flooded. Indicated by the index.
Last Flood Scan Length Indicates the size of the last flooding list of LSAs flooded and the maximum size of the flooding list. 1 LSA is transmitted at a time when OSPF pacing is enabled.
Last Flood Scan Time Indicates the time spent in the last flooding and the maximum time ever spent in flooding.
Neighbor Count Indicates the number of OSPF neighbors discovered on an interface.
Adjacent Neighbor Count Indicates the number of OSPF neighbors that have established FULL adjacency with the router. Adjacency means that their databases are fully synchronized.
Suppress Hello When an OSPF demand circuit is established over a dialup link that incur usage-based costs, periodic OSPF Hello packets are suppressed to prevent the link from remains always up.

No comments:

Post a Comment