Re: Confused about my home networking setup

Robert Harris wrote:

Hamad bin Turki Salami wrote:
Life used to be simple. I used to assign a static id in the 192.168.1.x
range to every box on my home LAN and I used two static id's for my
domain name server from my ISP, Comcast.

Then I got a message from Comcast, warning that I needed to change my
network settings to use DHCP and automatically get the dns
from the provider. That's when things started going haywire.

I have Linux boxes, Windows boxes, and Mac OS X boxes on my
home network. The Mac boxes were no problem at all. They kept
working like nothing changed. The Windows boxes are doing okay
as well, with some hiccups. The Linux boxes aren't faring well.
I'd appreciate any help in getting things back to normal.

Here's my setup: I have a cable modem taking the feed from Comcast.
That hooks to a Linksys wireless G router. The Linksys router has
a DHCP server built in. Since the Comcast change, I've allowed
the Linksys to hand out IP addresses and I've set all my clients
to get their IP addresses from DHCP.

The problem is, my Linux boxes can't find the other computers anymore.
I can't print at all (my printer is attached to a Windows box).
To use ssh, I need to log in to my Linksys router to find out
what IP addresses are leased. Then, while my Mac and Windows
boxes seem to be telling the DHCP server what their names are,
the Linux boxes aren't.

So here's my question:
How do I set up a dns functionality for my local LAN, so all
the machines know where each other are, even after their DHCP
leases expire and are reassigned? Can I just run my own dns server
and forget using Comcast's?

I'd rather run it on Windows or Mac, since I'm probably going to
phase out Linux in the near future. But running it on Linux in
the near term is possible.



You are confusing two DHCP servers.

1. Your ISP uses DHCP to give the ISP interface of your router an IP
address.

2. Your router uses DHCP to give your local machines IP addresses.

You didn't have to use DHCP on your local net just because your ISP
didn't give you a fixed IP address. But if you do,

Let me explain a little more what I think is going on. Maybe I'm
confused.

My router has always been using DHCP to get *its* IP address from
Comcast. That IP address is what anyone outside my LAN sees when any of
my machines communicates with them (because the router uses NAT). My
router has also been getting dns server addresses from Comcast. Until
now, those dns addresses have never changed, so I've just entered them
directly one each machine.

Recently, Comcast has moved the dns servers from the old addresses.
I don't know why. I don't know how often they'll change them in the
future.

The reason I'm using DHCP in my local LAN is that that way, the router
tells them the dns server addresses. Now, each individual machine could
use DHCP directly with Comcast to get the dns address, but I think
that's a bad idea. First, Comcast's official line is that it only
supports a single machine. If you have a LAN, you're supposed to use
some service from Comcast to set it up, and it probably only supports
Windows or some such bull***, so I'm not going to do that. Also, I
don't want the outside world to see into my LAN. I like being behind
a firewall with one IP address.

Now, getting the dns address and getting the IP address for the local
LAN are logically distinct operations. However, I have 4 or 5 operating
systems on my LAN, and I don't want to take the time to figure out how
to do complicated stuff on all of them. On Mac OS X, it's easy; you can
do it with the gui. You open the Networking preference panel and it
gives you the option of setting a static IP address *and* getting your
dns from DHCP. If it were that easy on Linux and Windows, I probably
wouldn't be here, but none of my Linux or Windows based systems have
that option through the gui. That means digging a little deeper, which
is complicated and time consuming to do for multiple systems. I am
willing to do the work once, on one system, to set up a dns server. I
assume after I do that, it would be simple to direct any of my machines
to it and be done with my problems.


A. Your router, which hands out your local IP addresses, presumably has
DNS functionality as well. So your local machines use the router as
their DNS server. Don't worry about it: the DHCP protocol will tell them
where their DNS server is.

Unfortunately, I don't see how to make my router serve as a local dns
server. Maybe it can, maybe it can't. If someone here is familiar with
the Linksys wireless G router and knows how to do it, I'd be grateful.

B. You can only see local machines that have active DHCP leases (if they
do not have fixed addresses). Your linux machines probably don't declare
their hostnames to DHCP by default so edit the file:

/etc/dhcp3/dhclient

(or something like it) suct that there is a line that says:

send host name myhost

(if the host name is myhost).

I hope that this helps.

Robert
.