dhcping(8) General Commands Manual dhcping(8)
dhcping - send a DHCP request to DHCP server to see if
it's up and running
dhcping [-v] [-q] [-i] [-r] -t maxwait -c client-
IP-address -s server-IP-address -h client-hardware-address
This command allows the system administrator to check if a
remote DHCP server is still functioning.
-v Verbose, print some information.
-i Use DHCPINFORM packets.
-r Use DHCPREQUEST packets (default behaviour).
-q Quiet, print nothing on the screen.
Maximum time to wait for an answer from the server in
seconds. Default is 3 seconds.
Request this IP address. Note that this is also the
IP address the answer will be sent to.
Send the DHCP packet to this IP address.
Use this hardware-address in the DHCP request. It can
be up to sixteen octets seperated by colons (i.e.
Use this IP address for the gateway IP address in the
DHCP packet. This option is currently broken.
If everything goes okay, it returns 0. If there went
something wrong, it returns 1.
This program should be installed setuid root or ran by
root only. See SECURITY for more information.
On your DHCP server, add these lines to the dhcpd.conf:
hardware ethernet ;
Then try it:
$ dhcping -c your monitoring host IP address \
-s your DHCP server IP address \
-h your monitor host mac address
It will either respond with "no answer" or "Got answer
from: your DHCP server IP address"
The DHCP server logfile will give:
DHCPREQUEST for 192.168.1.1 from 00:20:18:56:29:8f via ed0
DHCPACK on 192.168.1.1 to 00:20:18:56:29:8f via ed0
DHCPRELEASE of 192.168.1.1 from 00:20:18:56:29:8f via ed0 (found)
Running in DHCPINFORM mode with -i:
If you see "DHCPINFORM from 192.168.1.1 via xl0: not
authoritative for subnet 192.168.1.0", you should add the
authoritative statement to the subnet, See dhcpd.conf(5)
When running in very verbose mode, dhcping tries to dump
all data of the send and received DHCP packets. It will
first dump the packet in hex-format, then decodes the
header and finally the options.
HOW IT WORKS
The client either sends a DHCPREQUEST or DHCPINFORM packet
to the server and waits for an answer. Then, if a
DHCPREQUEST was send, it will send a DHCPRELEASE back to
This program is installed setuid root as it requires the
privileges to bind itself to port 68 (bootpc). Root
privileges are dropped as soon as the program has bound
itself to that port.
Currently (this may, or may not, change in the future) the
ISC DHCP daemon does not write leases with a fixed IP
address in the dhcpd.leases file.
DHCPINFORM packets can only be used on subnets the server
is authori- tative for. If the monitoring script runs on a
subnet the server isn't authoritative for, it should use
the DHCPREQUEST packets. I also experienced some problems
with ISC DHCPD v2 servers, but that is also in the README
The -V option is still working, but shouldn't be used for
debugging of the packets. Better use dhcpdump(8) for that,
which is available on my website. I wanted to remove it,
but decided only to do it from the documentation, not from
the code. Maybe I'll need it one day for debugging.
Edwin Groothuis, email@example.com
dhcpd(8), dhclient(8), dhcpd.conf(5), dhcpdump(8)
3rd Berkeley DistributionJanuari 27, 2002 dhcping(8)