1dhcping(8) General Commands Manual dhcping(8)
2
6 ddhhccppiinngg - send a DHCP request to DHCP server to see if it's up and
7 running
8
10 ddhhccppiinngg [--vv] [--qq] [--ii] [--rr] --tt maxwait --cc client-IP-address --ss server-
11 IP-address --hh client-hardware-address [--gg gateway-IP-address]
12
14 This command allows the system administrator to check if a remote DHCP
15 server is still functioning.
16 Options are:
18 --vv Verbose, print some information.
20 --ii Use DHCPINFORM packets.
22 --rr Use DHCPREQUEST packets (default behaviour).
24 --qq Quiet, print nothing on the screen.
26 --tt maxwait
28 Maximum time to wait for an answer from the server in seconds.
29 Default is 3 seconds.
30 --cc client-IP-address
32 Request this IP address. Note that this is also the IP address the
33 answer will be sent to.
34 --ss server-IP-address
36 Send the DHCP packet to this IP address.
37 --hh client-hardware-address
39 Use this hardware-address in the DHCP request. It can be up to
40 sixteen octets seperated by colons (i.e. 01:02:03:04)
41 --gg gateway-IP-address
43 Use this IP address for the gateway IP address in the DHCP packet.
44 This option is currently broken.
45
47 If everything goes okay, it returns 0. If there went something wrong,
48 it returns 1.
49
51 This program should be installed setuid root or ran by root only. See
52 SECURITY for more information.
53 On your DHCP server, add these lines to the dhcpd.conf:
55 host <your monitoring host FQDN> {
57 hardware ethernet <your monitor host mac address>;
58 fixed-address <your monitoring host IP address>;
59 }
60 Then try it:
62 $ dhcping -c your monitoring host IP address \
64 -s your DHCP server IP address \
65 -h your monitor host mac address
66 It will either respond with "no answer" or "Got answer from: your DHCP
68 server IP address"
69 The DHCP server logfile will give:
71 DHCPREQUEST for 192.168.1.1 from 00:20:18:56:29:8f via ed0
72 DHCPACK on 192.168.1.1 to 00:20:18:56:29:8f via ed0
73 DHCPRELEASE of 192.168.1.1 from 00:20:18:56:29:8f via ed0 (found)
74 Running in DHCPINFORM mode with --ii:
76 If you see "DHCPINFORM from 192.168.1.1 via xl0: not authoritative for
78 subnet 192.168.1.0", you should add the authoritative statement to the
79 subnet, See dhcpd.conf(5) for details.
80 When running in very verbose mode, ddhhccppiinngg tries to dump all data of
82 the send and received DHCP packets. It will first dump the packet in
83 hex-format, then decodes the header and finally the options.
84
86 The client either sends a DHCPREQUEST or DHCPINFORM packet to the
87 server and waits for an answer. Then, if a DHCPREQUEST was send, it
88 will send a DHCPRELEASE back to the server.
89
91 This program is installed setuid root as it requires the privileges to
92 bind itself to port 68 (bootpc). Root privileges are dropped as soon as
93 the program has bound itself to that port.
94
96 Currently (this may, or may not, change in the future) the ISC DHCP
97 daemon does not write leases with a fixed IP address in the
98 dhcpd.leases file.
99 DHCPINFORM packets can only be used on subnets the server is authori-
101 tative for. If the monitoring script runs on a subnet the server isn't
102 authoritative for, it should use the DHCPREQUEST packets. I also
103 experienced some problems with ISC DHCPD v2 servers, but that is also
104 in the README of it.
105 The --VV option is still working, but shouldn't be used for debugging of
107 the packets. Better use dhcpdump(8) for that, which is available on my
108 website. I wanted to remove it, but decided only to do it from the
109 documentation, not from the code. Maybe I'll need it one day for
110 debugging.
111
113 Edwin Groothuis, edwin@mavetju.org (http://www.mavetju.org)
114
116 dhcpd(8), dhclient(8), dhcpd.conf(5), dhcpdump(8)
1173rd Berkeley Distribution Januari 27, 2002 dhcping(8)