debug packet [interface number [vcd vcd-number] | vc vpi/vci | vc-name]
no debug packet [interface number [vcd vcd-number] | vc vpi/vci | vc-name]
interface number (Optional) interface or subinterface number. vcd vcd-number (Optional) Number of the virtual circuit designator (VCD). vc vpi/vci (Optional) VPI and VCI numbers of the VC. vc-name (Optional) Name of the PVC or SVC.
To display per-packet debugging output, use the debug packet privileged EXEC command. The no form of this command disables debugging output.
The debug packet command displays all process-level packets for both outbound and inbound packets. This command is useful for determining whether packets are being received and sent correctly. The output reports information online when a packet is received or a transmission is attempted.
For sent packets, the information is displayed only after the protocol data unit (PDU) is entirely encapsulated and a next hop VC is found. If information is not displayed, the address translation probably failed during encapsulation. When a next hop VC is found, the packet is displayed exactly as it will be presented on the wire. Having a display indicates that the packets are properly encapsulated for transmission.
For received packets, information is displayed for all incoming frames. The display can show whether the sending station properly encapsulates the frames. Because all incoming frames are displayed, this information is useful when performing back-to-back testing and corrupted frames cannot be dropped by an intermediary switch.
The debug packet command also displays the initial bytes of the actual PDU in hexadecimal. This information can be decoded only by qualified support or engineering personnel.
Because the debug packet command generates a substantial amount of output for every packet processed, use it only when traffic on the network is low, so other activity on the system is not adversely affected.
The following is sample output from the debug packet command:Router# debug packet 2/0.5(I): VCD:0x9 VCI:0x23 Type:0x0 SAP:AAAA CTL:03 OUI:000000 TYPE:0800 Length0x70 4500 002E 0000 0000 0209 92ED 836C A26E FFFF FFFF 1108 006D 0001 0000 0000 A5CC 6CA2 0000 000A 0000 6411 76FF 0100 6C08 00FF FFFF 0003 E805 DCFF 0105
The following two lines of output are the binary data, which are the contents of the protocol PDU before encapsulation: 4500 002E 0000 0000 0209 92ED 836C A26E FFFF FFFF 1108 006D 0001 0000 0000 A5CC 6CA2 0000 000A 0000 6411 76FF 0100 6C08 00FF FFFF 0003 E805 DCFF 0105
Router# debug packet Ethernet0: Unknown ARPA, src 0000.0c00.6fa4, dst ffff.ffff.ffff, type 0x0a0 data 00000c00f23a00000c00ab45, len 60 Serial3: Unknown HDLC, size 64, type 0xaaaa, flags 0x0F00 Serial2: Unknown PPP, size 128 Serial7: Unknown FRAME-RELAY, size 174, type 0x5865, DLCI 7a Serial0: compressed TCP/IP packet dropped
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