How would I do this?

Glenn Satchell Glenn.Satchell at
Tue Feb 10 22:59:40 UTC 2009

>Date: Tue, 10 Feb 2009 15:54:22 -0600
>From: E Johnson <ej.isc at>
>To: DHCP Users List <dhcp-users at>
>Subject: How would I do this?
>Sorry for the vague subject line.
>I have 2 situations that I am wondering if the DHCP Server can help me 
>deal with.
>First of all, I am a rookie.
>Situation 1...
>I have a notebook user who can connect to the network by way of wireless 
>or wired.  Sometimes he thinks he is having a problem with the wireless 
>connection and plugs in the wired connect, then of course nothing works.
>Is it possible for the DHCP Server to refuse to give an IP when one or 
>the other client already has one?  If he is connected wirelessly, then 
>the wired connection will not get an IP or vice versa.
>Situation 2...
>I have a notebook user who is a little technologically challenged.  When 
>she would travel outside the office we would have files that she needs 
>placed on her desktop or in My Documents folder.  So we have shortcuts 
>for these network shares.  The notebook user is able to connect to the 
>office network either by wireless or wired connection.
>Is it possible to tell the DHCP Server to give her the same IP when she 
>is connected by wire or wirelessly?  That way, we can use the same 
>network shortcuts to her all the time.
>I hope that I am making sense through all this.
>Eric Johnson

Hi Eric

Not sure about situation 1, probably needs some sort of conditional
statement coupled with "ignore booting;"

For situation 2 you can use a fixed address, eg:

host laptop_lan {
	# ethernet mac address here
	hardware ethernet aa:bb:cc:dd:ee:ff;
host laptop_wireless {
	# wireless mac address here
	hardware ethernet ff:ee:dd:cc:bb:aa;

Note the same IP address assigned both times.

The best documentation is the man pages, suggested reading is:

man dhcpd.conf
man dhcp-options
man dhcp-eval


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