Cisco Cisco IOS Software Release 12.4(2)XB6 Références techniques
-33
Book Title
OL-14681-01
Chapter Cisco Broadband Wireless Gateway 1.1 Command Reference, IOS Release 12.4(15)XL2
debug ip packet
Caution
The dump keyword is not fully supported and should be used only in collaboration with Cisco Technical
Support. Because of the risk of using significant CPU utilization, the dump keyword is hidden from the
user and cannot be seen using the “?” prompt. The length of the displayed packet information may
exceed the actual packet length and include additional padding bytes that do not belong to the IP packet.
Also note that the beginning of a packet may start at different locations in the dump output depending
on the specific router, interface type, and packet header processing that may have occurred before the
output is displayed.
Support. Because of the risk of using significant CPU utilization, the dump keyword is hidden from the
user and cannot be seen using the “?” prompt. The length of the displayed packet information may
exceed the actual packet length and include additional padding bytes that do not belong to the IP packet.
Also note that the beginning of a packet may start at different locations in the dump output depending
on the specific router, interface type, and packet header processing that may have occurred before the
output is displayed.
Examples
The following is sample output from the debug ip packet command:
Router# debug ip packet
IP packet debugging is on
IP: s=172.69.13.44 (Fddi0), d=10.125.254.1 (Serial2), g=172.69.16.2, forward
IP: s=172.69.1.57 (Ethernet4), d=10.36.125.2 (Serial2), g=172.69.16.2, forward
IP: s=172.69.1.6 (Ethernet4), d=255.255.255.255, rcvd 2
IP: s=172.69.1.55 (Ethernet4), d=172.69.2.42 (Fddi0), g=172.69.13.6, forward
IP: s=172.69.89.33 (Ethernet2), d=10.130.2.156 (Serial2), g=172.69.16.2, forward
IP: s=172.69.1.27 (Ethernet4), d=172.69.43.126 (Fddi1), g=172.69.23.5, forward
IP: s=172.69.1.27 (Ethernet4), d=172.69.43.126 (Fddi0), g=172.69.13.6, forward
IP: s=172.69.20.32 (Ethernet2), d=255.255.255.255, rcvd 2
IP: s=172.69.1.57 (Ethernet4), d=10.36.125.2 (Serial2), g=172.69.16.2, 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.
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.
describes the significant fields shown in the display.
The following is sample output from the debug ip packet command enabled with the detail keyword:
Router# debug ip packet detail
IP packet debugging is on (detailed)
001556: 19:59:30: CEF: Try to CEF switch 10.4.9.151 from FastEthernet0/0
Table 8
debug ip packet Field Descriptions
Field
Description
IP:
Indicates that this is an IP packet.
s=172.69.13.44 (Fddi0)
Indicates the source address of the packet and the name of the
interface that received the packet.
interface that received the packet.
d=10.125.254.1 (Serial2)
Indicates the destination address of the packet and the name of the
interface (in this case, S2) through which the packet is being sent out
on the network.
interface (in this case, S2) through which the packet is being sent out
on the network.
g=172.69.16.2
Indicates the address of the next-hop gateway.
forward
Indicates that the router is forwarding the packet. If a filter denies a
packet, “access denied” replaces “forward,” as shown in the last line
of output.
packet, “access denied” replaces “forward,” as shown in the last line
of output.