Using OSPF debug Commands

The debug ip ospf events output shown in Example 4-6 might appear if any of the following situations occur:

■ The IP subnet masks for the routers on the same network do not match.

■ The OSPF hello interval for the router does not match the OSPF hello interval that is configured on a neighbor.

■ The OSPF dead interval for the router does not match the OSPF dead interval that is configured on a neighbor.

If a router that is configured for OSPF routing is not seeing an OSPF neighbor on an attached network, perform the following tasks:

■ Ensure that both routers have been configured with the same IP subnet mask and that the OSPF hello interval and dead intervals match on both routers.

■ Ensure that both neighbors are part of the same area number and area type.

■ Ensure that authentication type and passwords match.

In Example 4-6, which shows output from the debug ip ospf events command, the neighbor router and this router are not part of a stub area, denoted by the mismatched E bit. That is, one router is configured for the area to be a transit area, and the other router is configured for the area to be a stub area, as explained in RFC 2328.

Example 4-6 debug ip ospf events Command Output RouterX#debug ip ospf events

OSPF:hello with invalid timers on interface Ethernet0 hello interval received 10 configured 10 net mask received configured dead interval received 40 configured 30

OSPF: hello packet with mismatched E bit

To display information about each OSPF packet that is received, use the debug ip ospf packet privileged EXEC command. The no form of this command disables the debugging output.

The debug ip ospf packet command produces one set of information for each packet that is received. The output varies slightly depending on which authentication is used. The table shows sample output from the debug ip ospf packet command when Message Digest 5 (MD5) authentication is used. Example 4-7 shows an OSPF message received and displayed when using this debug command.

Example 4-7 debug ip ospf packet Command Output

RouterX# debug

ip ospf


OSPF: rcv. v:2

t:1 l:48



).0 chk:0


2 keyid:1 seq:0x0

Table 4-5 describes the significance of the fields in this output. Table 4-5 debug ip ospf packet Fields




OSPF version


OSPF packet type; possible packet types are as follows:

• Data description

• Link-state request

• Link-state update

• Link-state acknowledgment


OSPF packet length in bytes


OSPF router ID


OSPF area ID


OSPF checksum


OSPF authentication type; possible authentication types are as follows: 0: No authentication 1: Simple password 2: MD5


OSPF authentication key


MD5 key ID


Sequence number

+1 0

Post a comment