| 1 |
root |
1.1 |
# |
| 2 |
|
|
# $Id: dhcping.pod,v 1.1 2002/01/27 01:57:15 mavetju Exp $ |
| 3 |
|
|
# |
| 4 |
|
|
|
| 5 |
|
|
=head1 NAME |
| 6 |
|
|
|
| 7 |
|
|
B<dhcping> - send a DHCP request to DHCP server to see if it's up and running |
| 8 |
|
|
|
| 9 |
|
|
=head1 SYNOPSIS |
| 10 |
|
|
|
| 11 |
|
|
B<dhcping> |
| 12 |
|
|
[B<-v>] [B<-q>] [B<-i>] [B<-r>] |
| 13 |
|
|
B<-t> I<maxwait> |
| 14 |
|
|
B<-c> I<client-IP-address> |
| 15 |
|
|
B<-s> I<server-IP-address> |
| 16 |
|
|
B<-h> I<client-hardware-address> |
| 17 |
|
|
[B<-g> I<gateway-IP-address>] |
| 18 |
|
|
|
| 19 |
|
|
=head1 DESCRIPTION |
| 20 |
|
|
|
| 21 |
|
|
This command allows the system administrator to check if a remote |
| 22 |
|
|
DHCP server is still functioning. |
| 23 |
|
|
|
| 24 |
|
|
Options are: |
| 25 |
|
|
|
| 26 |
|
|
=over |
| 27 |
|
|
|
| 28 |
|
|
=item B<-v> |
| 29 |
|
|
|
| 30 |
|
|
Verbose, print some information. |
| 31 |
|
|
|
| 32 |
|
|
=item B<-i> |
| 33 |
|
|
|
| 34 |
|
|
Use DHCPINFORM packets. |
| 35 |
|
|
|
| 36 |
|
|
=item B<-r> |
| 37 |
|
|
|
| 38 |
|
|
Use DHCPREQUEST packets (default behaviour). |
| 39 |
|
|
|
| 40 |
|
|
=item B<-q> |
| 41 |
|
|
|
| 42 |
|
|
Quiet, print nothing on the screen. |
| 43 |
|
|
|
| 44 |
|
|
=item B<-t> I<maxwait> |
| 45 |
|
|
|
| 46 |
|
|
Maximum time to wait for an answer from the server in seconds. |
| 47 |
|
|
Default is 3 seconds. |
| 48 |
|
|
|
| 49 |
|
|
=item B<-c> I<client-IP-address> |
| 50 |
|
|
|
| 51 |
|
|
Request this IP address. Note that this is also the IP address the |
| 52 |
|
|
answer will be sent to. |
| 53 |
|
|
|
| 54 |
|
|
=item B<-s> I<server-IP-address> |
| 55 |
|
|
|
| 56 |
|
|
Send the DHCP packet to this IP address. |
| 57 |
|
|
|
| 58 |
|
|
=item B<-h> I<client-hardware-address> |
| 59 |
|
|
|
| 60 |
|
|
Use this hardware-address in the DHCP request. It can be up to |
| 61 |
|
|
sixteen octets seperated by colons (i.e. 01:02:03:04) |
| 62 |
|
|
|
| 63 |
|
|
=item B<-g> I<gateway-IP-address> |
| 64 |
|
|
|
| 65 |
|
|
Use this IP address for the gateway IP address in the DHCP packet. |
| 66 |
|
|
This option is currently broken. |
| 67 |
|
|
|
| 68 |
|
|
=back |
| 69 |
|
|
|
| 70 |
|
|
=head1 RETURN VALUES |
| 71 |
|
|
|
| 72 |
|
|
If everything goes okay, it returns 0. If there went something |
| 73 |
|
|
wrong, it returns 1. |
| 74 |
|
|
|
| 75 |
|
|
=head1 SETUP |
| 76 |
|
|
|
| 77 |
|
|
This program should be installed setuid root or ran by root only. |
| 78 |
|
|
See SECURITY for more information. |
| 79 |
|
|
|
| 80 |
|
|
On your DHCP server, add these lines to the dhcpd.conf: |
| 81 |
|
|
|
| 82 |
|
|
host <your monitoring host FQDN> { |
| 83 |
|
|
hardware ethernet <your monitor host mac address>; |
| 84 |
|
|
fixed-address <your monitoring host IP address>; |
| 85 |
|
|
} |
| 86 |
|
|
|
| 87 |
|
|
Then try it: |
| 88 |
|
|
|
| 89 |
|
|
$ dhcping -c I<your monitoring host IP address> \ |
| 90 |
|
|
-s I<your DHCP server IP address> \ |
| 91 |
|
|
-h I<your monitor host mac address> |
| 92 |
|
|
|
| 93 |
|
|
It will either respond with "no answer" or "Got answer from: I<your |
| 94 |
|
|
DHCP server IP address>" |
| 95 |
|
|
|
| 96 |
|
|
The DHCP server logfile will give: |
| 97 |
|
|
S<DHCPREQUEST for 192.168.1.1 from 00:20:18:56:29:8f via ed0> |
| 98 |
|
|
S<DHCPACK on 192.168.1.1 to 00:20:18:56:29:8f via ed0> |
| 99 |
|
|
S<DHCPRELEASE of 192.168.1.1 from 00:20:18:56:29:8f via ed0 (found)> |
| 100 |
|
|
|
| 101 |
|
|
Running in DHCPINFORM mode with B<-i>: |
| 102 |
|
|
|
| 103 |
|
|
If you see "DHCPINFORM from 192.168.1.1 via xl0: not authoritative |
| 104 |
|
|
for subnet 192.168.1.0", you should add the authoritative statement |
| 105 |
|
|
to the subnet, See dhcpd.conf(5) for details. |
| 106 |
|
|
|
| 107 |
|
|
When running in very verbose mode, B<dhcping> tries to dump all |
| 108 |
|
|
data of the send and received DHCP packets. It will first dump the |
| 109 |
|
|
packet in hex-format, then decodes the header and finally the |
| 110 |
|
|
options. |
| 111 |
|
|
|
| 112 |
|
|
=head1 HOW IT WORKS |
| 113 |
|
|
|
| 114 |
|
|
The client either sends a DHCPREQUEST or DHCPINFORM packet to the |
| 115 |
|
|
server and waits for an answer. Then, if a DHCPREQUEST was send, |
| 116 |
|
|
it will send a DHCPRELEASE back to the server. |
| 117 |
|
|
|
| 118 |
|
|
=head1 SECURITY |
| 119 |
|
|
|
| 120 |
|
|
This program is installed setuid root as it requires the privileges |
| 121 |
|
|
to bind itself to port 68 (bootpc). Root privileges are dropped as |
| 122 |
|
|
soon as the program has bound itself to that port. |
| 123 |
|
|
|
| 124 |
|
|
=head1 BUGS |
| 125 |
|
|
|
| 126 |
|
|
Currently (this may, or may not, change in the future) the ISC DHCP |
| 127 |
|
|
daemon does not write leases with a fixed IP address in the |
| 128 |
|
|
dhcpd.leases file. |
| 129 |
|
|
|
| 130 |
|
|
DHCPINFORM packets can only be used on subnets the server is authori- |
| 131 |
|
|
tative for. If the monitoring script runs on a subnet the server |
| 132 |
|
|
isn't authoritative for, it should use the DHCPREQUEST packets. I |
| 133 |
|
|
also experienced some problems with ISC DHCPD v2 servers, but that |
| 134 |
|
|
is also in the README of it. |
| 135 |
|
|
|
| 136 |
|
|
The B<-V> option is still working, but shouldn't be used for |
| 137 |
|
|
debugging of the packets. Better use dhcpdump(8) for that, which |
| 138 |
|
|
is available on my website. I wanted to remove it, but decided only |
| 139 |
|
|
to do it from the documentation, not from the code. Maybe I'll need |
| 140 |
|
|
it one day for debugging. |
| 141 |
|
|
|
| 142 |
|
|
=head1 AUTHOR |
| 143 |
|
|
|
| 144 |
|
|
Edwin Groothuis, edwin@mavetju.org (http://www.mavetju.org) |
| 145 |
|
|
|
| 146 |
|
|
=head1 SEE ALSO |
| 147 |
|
|
|
| 148 |
|
|
dhcpd(8), dhclient(8), dhcpd.conf(5), dhcpdump(8) |
