Comments on: How do I find out my DHCP server address?

By: KoteswaraRao

KoteswaraRao — Mon, 10 Aug 2009 06:27:44 +0000

sir

iam kotesh pleces data to dhcp and dns server

By: Saurabh

Saurabh — Sat, 22 Nov 2008 17:00:27 +0000

Thanks for the good post admin
and thanks to robert for telling how to get to know the dhcp server ip when their is no leases

my case was also same as robert explain
thanks

By: Shylesh

Shylesh — Tue, 26 Aug 2008 06:17:14 +0000

Mine is at
/var/lib/dhclient/dhclient-eth0.leases

so the server would be
grep dhcp-server /var/lib/dhclient/dhclient-eth0.leases

By: Ryan

Ryan — Tue, 05 Aug 2008 15:29:42 +0000

Run this to get just your DHCP Server name:

cat dhclient.leases | grep dhcp-server | uniq | cut -d” ” -f5 | cut -d”;” -f1

By: Marko

Marko — Mon, 17 Mar 2008 15:13:03 +0000

I need to know just my DHCP server address value from code, so if there is some script or a neath way to do it, without parsing the dhclient.leasing file?

By: Marko

Marko — Mon, 17 Mar 2008 15:04:20 +0000

How can I get just DHCPACK value from code(C,C++) ?

By: vivek

vivek — Tue, 11 Dec 2007 07:54:25 +0000

Robert,

When you run dhclient eth0, it always show DHCP address on screen, just look for DHCPACK (no need to run tcpdump)

dhclient ra0
There is already a pid file /var/run/dhclient.pid with pid 134519120
Internet Systems Consortium DHCP Client V3.0.5
Copyright 2004-2006 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

Listening on LPF/ra0/00:17:9a:0a:f6:44
Sending on   LPF/ra0/00:17:9a:0a:f6:44
Sending on   Socket/fallback
DHCPDISCOVER on ra0 to 255.255.255.255 port 67 interval 6
DHCPOFFER from 192.168.1.1
DHCPREQUEST on ra0 to 255.255.255.255 port 67
DHCPACK from 192.168.1.1
bound to 192.168.1.106 -- renewal in 39175 seconds.

By: Robert de Bock

Robert de Bock — Mon, 10 Dec 2007 15:29:16 +0000

In case you don’t have a lease, you could (but it’s more work) request a lease with dhclient(8) and use tcpdump(8) to see what server answered. Use something like this in one terminal:
# tcpdump -i eth0 port 67 or port 68
And something like this in a second terminal:
# dhclient eth0
If you are lucky, dhclient will even tell you what the DHCP server is.

Regards, Robert.