dhcpdump8

Usage

Overview

This command listens on a network interface to display the dhcp-packets for easier checking and debugging.

Usage

dhcpdump -i /dev/fxp0

If you want to filter a specific Client Hardware Address (CHADDR), then you can specify it as a regular expression:

dhcpdump -i /dev/fxp0 -h ^00:c0:4f

This will display only the packets with Client Hardware Addresses which start with 00:c0:4f.

Option -H will additionally show full packet hex dump.

Instead of getting live data from an interface, a pcap dump file can be used:

dhcpdump -r pcapfile

Output

  TIME: 15:45:02.084272
    IP: 0.0.0.0.68 (0:c0:4f:82:ac:7f) > 255.255.255.255.67 (ff:ff:ff:ff:ff:ff)
    OP: 1 (BOOTPREQUEST)
 HTYPE: 1 (Ethernet)
  HLEN: 6
  HOPS: 0
   XID: 28f61b03
  SECS: 0
 FLAGS: 0
CIADDR: 0.0.0.0
YIADDR: 0.0.0.0
SIADDR: 0.0.0.0
GIADDR: 0.0.0.0
CHADDR: 00:c0:4f:82:ac:7f:00:00:00:00:00:00:00:00:00:00
 SNAME: .
 FNAME: .
OPTION:  53 (  1) DHCP message type         3 (DHCPREQUEST)
OPTION:  54 (  4) Server identifier         130.139.64.101
OPTION:  50 (  4) Request IP address        130.139.64.143
OPTION:  55 (  7) Parameter Request List      1 (Subnet mask)
                                              3 (Routers)
                                             58 (T1)
                                             59 (T2)

At the option field, the first field is the value of the option, the second one (between brackets) is the length of the option-datafield, the third field is the name of the option, the fourth field is the data of the option.

Return values

Always 0.

Notes

Privileged access is often needed for accessing the interface.

Thanks to

Ralph Droms and Ted Lemons "The DHCP Handbook", ISBN 1-57870-137-6.

Peter Apian-Bennewitz <[email protected]> for his Client Hardware Address filtering