Re: Forcing specific IP address with DHCP

On Thu, 17 Apr 2008 11:36:53 -0500
Michael Shuler <michael@xxxxxxxxxxxxxx> wrote:

On 04/17/2008 09:31 AM, Celejar wrote:
I find myself in a bizarre networking predicament. I need to have
a server (henceforth 'edith') accept incoming connections (e.g. ssh)
from the Internet. edith is behind a home gateway / router / switch
( Trendware / Trendnet TEW-452BRP [0] - henceforth 'gwen'). gwen will
forward specific ports to specific private, internal IP addresses, but
bizarrely, it seems to provide no facility for ensuring that a specific
host will be assigned, via DHCP, a particular IP address.

Not such a bizarre thing - I do this for several servers running behind
a Debian router/firewall server for my home connection. I don't know
about the particular router you are using, but if it does not allow
MAC->IP mapping, I think assuming that it has no dynamic DHCP client is
fair :P

I don't quite follow you here. What's a dynamic DHCP client? gwen has
both a DHCP server for the LAN, as well as a client for getting its own
external IP address from the ISP. Can you elaborate?

What would you do in this situation (besides getting a different router
or using a general purpose computer as one)?

Stick a Debian box behind your ISP modem and set it up as your gateway
and DHCP server - then run ddclient with a service like DynDNS
(apt-cache show ddclient) - I do this at home, at work, on my laptop - I
can always get to the machines I might need by hostname - who cares what
the IP is :)

For logistical reasons, alternating the current topology of my network,
specifically the connection of the modem to the router and the physical
location of them both, is not currently practical. I actually do use
ddclient with DynDNS, to reach edith using DNS from the Internet.
ddclient runs on edith; it reads gwen's external IP address from the
relevant status page on gwen's web interface, and then records it with
DynDNS. DynDNS translates the DNS name to gwen's external IP address,
and gwen then forwards the incoming connections to edith. Did you mean
something else?

Thanks for the suggestions.

Kind Regards,
Michael Shuler

Celejar
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