debug ip packet




debug ip packet [access-list-number]

no debug ip packet [access-list-number]

Syntax Description:


(Optional) The IP access list number that you can specify. If the datagram is not permitted by that access list, the related debugging output is suppressed.

Command Description:


To display general IP debugging information and IP security option (IPSO) security transactions, use the

debug ip packet privileged EXEC command. The no form of this command disables debugging output.


If a communication session is closing when it should not be, an end-to-end connection problem can be

the cause. The debug ip packet command is useful for analyzing the messages traveling between the

local and remote hosts.


IP debugging information includes packets received, generated, and forwarded. Fast-switched packets

do not generate messages.


IPSO security transactions include messages that describe the cause of failure each time a datagram fails

a security test in the system. This information is also sent to the sending host when the router

configuration allows it.


Caution:  Because the debug ip packet command generates a substantial amount of output, use it only when

traffic on the IP network is low, so other activity on the system is not adversely affected.


The following is sample output from the debug ip packet command:


Router# debug ip packet

IP: s= (Fddi0), d= (Serial2), g=, forward

IP: s= (Ethernet4), d= (Serial2), g=, forward

IP: s= (Ethernet4), d=, rcvd 2

IP: s= (Ethernet4), d= (Fddi0), g=, forward

IP: s= (Ethernet2), d= (Serial2), g=, forward

IP: s= (Ethernet4), d= (Fddi1), g=, forward

IP: s= (Ethernet4), d= (Fddi0), g=, forward

IP: s= (Ethernet2), d=, rcvd 2

IP: s= (Ethernet4), d= (Serial2), g=, access denied


The output shows two types of messages that the debug ip packet command can produce; the first line

of output describes an IP packet that the router forwards, and the third line of output describes a packet

that is destined for the router. In the third line of output, rcvd 2 indicates that the router decided to receive

the packet.



Related Commands:


� Cisco Systems, Inc. 2001, 2002, 2003
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