man dhcpdump (Commandes) - DHCP packet dumper
NAME
dhcpdump - DHCP packet dumper
SYNOPSIS
dhcpdump [-h regular-expression]
DESCRIPTION
This command parses the output of tcpdump to display the dhcp-packets for easier checking and debugging.
USAGE
tcpdump -lenx -s 1500 port bootps or port bootpc | dhcpdump
If you want to filter a specific Client Hardware Address (CHADDR), then you can specifiy it as a regular expressions:
tcpdump -lenx -s 1500 port bootps or port bootpc | dhcpdump -h ^00:c0:4f
This will display only the packets with Client Hardware Addresses which start with 00:c0:4f.
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 tcpdump.
BUGS
Not all the parameter options are printed verbose, because of lack of documentation. Not all the options are tested, because of lack of clients/servers with these options. If you have a dump of one of them, please send them to me and I'll incorperate them.
THANKS TO
Ralph Droms and Ted Lemons The DHCP Handbook, ISBN 1-57870-137-6.
Peter Apian-Bennewitz <apian@ise.fhg.de> for his Client Hardware Address filtering
AUTHOR
Edwin Groothuis, edwin@mavetju.org (http://www.mavetju.org)