dhcptest

This is a DHCP test tool. It can send DHCP discover packets, and listen for DHCP replies.

The tool is cross-platform, although you will need to compile it yourself for non-Windows platforms.

The tool is written in the D Programming Language.

Download

You can download a compiled Windows executable from my website, here.

The latest development build for Windows can be downloaded from GitHub Actions.

Building

With DMD (or another D compiler) installed, run:

$ dmd dhcptest.d

Usage

By default, dhcptest starts in interactive mode. It will listen for DHCP replies, and allow sending DHCP discover packets using the "d" command. Type help in interactive mode for more information.

If you do not receive any replies, try using the --bind option (or --iface on Linux) to bind to a specific local interface.

The program can also run in automatic mode if the --query switch is specified on the command line.

An example command line to automatically send a discover packet and explicitly request option 43, wait for a reply, then print just that option:

dhcptest --quiet --query --request 43 --print-only 43

Options can also be specified by name:

dhcptest --quiet --query \
     --request    "Vendor Specific Information" \
     --print-only "Vendor Specific Information"

Query mode will report the first reply recieved. To automatically send a discover packet and wait for all replies before the timeout, use --wait. For additional resilience against dropped packets on busy networks, consider using the --tries and --timeout switches:

dhcptest --quiet --query --wait --tries 5 --timeout 10

You can spoof the Vendor Class Identifier, or send additional DHCP options with the request packet, using the --option switch:

dhcptest --query --option "60=Initech Groupware"

Option 82 (Relay Agent Information) can be specified as follows:

dhcptest --query --option "Relay Agent Information=agentCircuitID=\"foo\", agentRemoteID=\"bar\""

Run dhcptest --help for further details and additional command-line parameters.

For a list and description of DHCP options, see RFC 2132.

License

dhcptest is available under the Boost Software License 1.0.

Changelog

dhcptest v0.9 (2023-03-31)

• Add option 121 (contributed by Andrey Baranov)
• Add options 80, 100, 101, 108, 114, 116, 118, 249, and 252 (contributed by Rob Gill
• Fix encoding/decoding options 43 and 82

dhcptest v0.8 (2023-03-24)

• Add --iface option for Linux
• Add support for Linux raw sockets (--raw)
• Add --bind, --target, and --target-port options
• Add --giaddr option (contributed by pcsegal)
• Improve formatting and parsing of many options

dhcptest v0.7 (2017-08-03)

• Refactor and improve option value parsing

• Allow specifying all supported format types in both --option and --print-only switches

• Allow specifying DHCP option types by name as well as by number

• Allow overriding the request type option. E.g., you can now send 'request' (instead of 'discover') packets using:

  --option "DHCP Message Type=request"

• Add formatting support for options 42 (Network Time Protocol Servers Option) and 82 (Relay Agent Information)

• Change how timeouts are handled:

  • Always default to some finite timeout (not just when --tries and --wait are absent), but still allow waiting indefinitely if 0 is specified.
  • Increase default timeout from 10 to 60 seconds.

dhcptest v0.6 (2017-08-02)

• Add --secs switch
• Contributed by Darren White:
  • Add --wait switch
  • The --print-only switch now understands output formatting: --print-only "N[hex]" will output the value as a zero padded hexadecimal string of bytes. --print-only "N[ip]" will output the value as an IP address.
• Don't print stack trace on errors

dhcptest v0.5 (2014-11-26)

• The --option switch now understands hexadecimal or IPv4-dotted-quad formatting:
  --option "N[hex]=XX XX XX ..." or --option "N[IP]=XXX.XXX.XXX.XXX"

dhcptest v0.4 (2014-07-21)

• Add switches: --tries, --timeout, --option

dhcptest v0.3 (2014-04-05)

• Add switches: --mac, --quiet, --query, --request, --print-only
• Print program messages to standard error

dhcptest v0.2 (2014-03-25)

• License under Boost Software License 1.0
• Add documentation
• Add --help switch
• Add --bind switch to specify the interface to bind on
• Print time values in human-readable form
• Heuristically detect and print ASCII strings in unknown options
• Add option names from RFC 2132
• Add help and quit commands
• Add MAC address option to discover command

dhcptest v0.1 (2013-01-10)

• Initial release