How would I do this?

Sten Carlsen sten at
Wed Feb 11 08:08:46 UTC 2009


There can be differences depending on the actual systems used. I use a
MAC, and I use the solution outlined with two host statements and the
same IP address. If I am inside my own network, I can switch by plugging
in or out the cable, I have coverage for WLAN in larger area than I can
find a cable, nothing gets disrupted, not even ongoing downloads.

I assume you want this to work with windows, you need to test for your
setup. Windows may behave differently than my setup; the time it takes
to discover a newly connected interface and the priorities between
interfaces has to be taken into account. Also your geography looks
different, so if you can get to a situation where WLAN coverage
disappears before you can attach a cable, the usual disruptions apply.

Bind provides DNS service and using views allows the inside users to use
internal addresses and external users to use public addresses for the
same servers and services. It seems that you don't need that now. Dhcp
will be able to communicate with bind so name resolution automagically
works, but let us get back to that when/if you need that.

E Johnson wrote:
> It sounds like this DHCP Server is very forgiving, the one in the
> router, currently being used, is not.
> "use views with bind", I sorry but I don't understand, also if it
> makes a difference, I am only concerned about the network connections
> while inside the office.  Outside connections aren't allowed, but I'm
> sure that will change someday.
> Thanks,
> Eric Johnson
> Sten Carlsen wrote:
>> Why not use same solution in both cases? I use that at home.
>> For sit. 1: downloads should continue even if the cable is
>> inserted/removed in the middle of a download (does for me).
>> For situation 2: If you use views with bind, the names will resolve
>> different depending on the user being outside or inside, that way
>> correct link will always be available.
>> Glenn Satchell wrote:
>>>> 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.
>>>> Thanks,
>>>> 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;
>>>     fixed-address;
>>> }
>>> host laptop_wireless {
>>>     # wireless mac address here
>>>     hardware ethernet ff:ee:dd:cc:bb:aa;
>>>     fixed-address;
>>> }
>>> 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
>>> regards,
>>> -glenn
>>> _______________________________________________
>>> dhcp-users mailing list
>>> dhcp-users at
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Best regards

Sten Carlsen

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