[nSLUG] DHCP and name resolution question

Dop Ganger nslug at fop.ns.ca
Thu May 5 10:57:17 ADT 2005

On Thu, 5 May 2005, Mike Spencer wrote:

> So I got a DHCP client working by changing one line in an rc.d file.
> Nothing to it. But there's a problem on my LAN that I don't quite get.
> (Isn't there always? :-)
>    My main box and another (bogus & alien) are connected to a router
>    by cable and have fixed IP addresses assigned.
>    If the laptop (moby) runs a DHCP client over wireless, the
>    (wireless) *router* itself has a DHCP server and assigns an
>    address to moby.
>    So far, so good. I can reach bogus and alien *from* moby, say,
>    with ping or telnet or "mount bogus:/".
>    BUT bogus and alien have no way of knowing what IP address moby
>    has.
> Is there some general way to deal with this?

I'm assuming that the router is doing NAT, so the wired machines all see 
the same IP address for all machines behind the router. If the router has 
a switch portion on it, plug the cable going to your LAN into that instead 
of the LAN portion, then disable the DHCP server on the wireless router. 
This will mean that the LAN is running directly on the local switch 
instead of being routed.

Alternatively, see if there's an option to configure the wireless router 
to run as a bridge instead of a router, and enable that. Note that this 
can be rather vaguely worded - I think my Belkin router says something 
like "run solely as an access point". This will set up the wireless router 
to do nothing more than forward packets between the wired and wireless 
LAN, including DHCP, which will allow you to set up a configuration stanza 
for your laptop's MAC address in the dhcpd.conf.

Note that both these solutions can be a security risk unless you have 
measures to control access, but I recall you mentioning that this isn't a 
major issue in your location.

Cheers... Dop.


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