dhcping(8)           General Commands Manual           dhcping(8)



NAME
       dhcping - send a DHCP request to DHCP server to see if
       it's up and running

SYNOPSIS
       dhcping [-v] [-q] [-i] [-r] -t maxwait -c client-
       IP-address -s server-IP-address -h client-hardware-address
       [-g gateway-IP-address]

DESCRIPTION
       This command allows the system administrator to check if a
       remote DHCP server is still functioning.

       Options are:

       -v   Verbose, print some information.

       -i   Use DHCPINFORM packets.

       -r   Use DHCPREQUEST packets (default behaviour).

       -q   Quiet, print nothing on the screen.

       -t maxwait
            Maximum time to wait for an answer from the server in
            seconds.  Default is 3 seconds.

       -c client-IP-address
            Request this IP address. Note that this is also the
            IP address the answer will be sent to.

       -s server-IP-address
            Send the DHCP packet to this IP address.

       -h client-hardware-address
            Use this hardware-address in the DHCP request. It can
            be up to sixteen octets seperated by colons (i.e.
            01:02:03:04)

       -g gateway-IP-address
            Use this IP address for the gateway IP address in the
            DHCP packet.  This option is currently broken.

RETURN VALUES
       If everything goes okay, it returns 0. If there went
       something wrong, it returns 1.

SETUP
       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:

         host  {
            hardware ethernet ;
            fixed-address     ;
         }

       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)
       for details.

       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
       the server.

SECURITY
       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.

BUGS
       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
       of it.

       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.

AUTHOR
       Edwin Groothuis, edwin@mavetju.org
       (http://www.mavetju.org)

SEE ALSO
       dhcpd(8), dhclient(8), dhcpd.conf(5), dhcpdump(8)
























3rd Berkeley DistributionJanuari 27, 2002              dhcping(8)