Two DHCP servers on the network

This may not be exactly a Linux question, but I will ask anyway. My
home network has a business cable modem thyat also doubles as a DHCP
server. Note that my network has statis IPs for servers and a bunch of
workstations with private 10.* addresses.

I tried making my linux server be a DHCP server, but the cable modem
seems to take precedence. The problem with addresses assigned by the
sable modem is that they act as if they were outside my home network
and do not reach my other NATTed workstations.

I want to know if I can somehow bump up the priority of my linux
server's DHCP server. I do like that if it is down dfor any reason,
the cable modem takes over, but I want it to have lower precedence.

thanks

i

Ignoramus6796 <(E-Mail Removed)> wrote:
> seems to take precedence. The problem with addresses assigned by the
> cable modem is that they act as if they were outside my home network
> and do not reach my other NATTed workstations.

Point your browser to the address of the cable modem. You will
usually find an option to disable the DHCP server, or alternatively you
can change the range of addresses that it allocates, saving the need to
run a separate DHCP server on the Linux machine.

Regards,

Mark.

--
Mark Hobley,
393 Quinton Road West,
Quinton, BIRMINGHAM.
B32 1QE.

On 2008-01-02, Mark Hobley <(E-Mail Removed)> wrote:
> Ignoramus6796 <(E-Mail Removed)> wrote:
>> seems to take precedence. The problem with addresses assigned by the
>> cable modem is that they act as if they were outside my home network
>> and do not reach my other NATTed workstations.
>
> Point your browser to the address of the cable modem. You will
> usually find an option to disable the DHCP server, or alternatively you
> can change the range of addresses that it allocates, saving the need to
> run a separate DHCP server on the Linux machine.

After some clearer thinking, I realized that this is not as big
problem as I thought originally. The DHCP managed machines are going
to basically be laptops (mine and my wife's), and I do not care too
much if they cannot reach our home computers with private addresses.

i

In comp.os.linux.misc Ignoramus6796 <(E-Mail Removed)> wrote:
> My home network has a business cable modem thyat also doubles as a
> DHCP server [...]

> I tried making my linux server be a DHCP server, but the cable modem
> seems to take precedence. [...]

If you really want/need your linux server to be a DHCP server, then turn
off the DHCP feature of your cable modem. You should not have two DHCP
servers handling the same network segment[*].

What were you hoping to achieve by using the linux box as a DHCP server?

Chris
[*] Unless you /really/ know what you're doing

On 2008-01-02, Chris Davies <chris-(E-Mail Removed)> wrote:
> In comp.os.linux.misc Ignoramus6796 <(E-Mail Removed)> wrote:
>> My home network has a business cable modem thyat also doubles as a
>> DHCP server [...]
>
>> I tried making my linux server be a DHCP server, but the cable modem
>> seems to take precedence. [...]
>
> If you really want/need your linux server to be a DHCP server, then turn
> off the DHCP feature of your cable modem. You should not have two DHCP
> servers handling the same network segment[*].
>
> What were you hoping to achieve by using the linux box as a DHCP server?

I have an internal 10.* network that uses my linux server as a NATting
gateway. My linux box is a routing amd masquerading server for those
machines.

Plus, this way it can use access control to shared drives with pirated
movies, etc based on IP.

In any case, I think that what I have now is OK, since the DHCP
clients are laptops that do not need to connect to other 10.*
machines.

i

> This may not be exactly a Linux question, but I will ask anyway. My
> home network has a business cable modem thyat also doubles as a DHCP
> server. Note that my network has statis IPs for servers and a bunch of
> workstations with private 10.* addresses.

> I tried making my linux server be a DHCP server, but the cable modem
> seems to take precedence. The problem with addresses assigned by the
> sable modem is that they act as if they were outside my home network
> and do not reach my other NATTed workstations.

I must say I don't understand your setup. You seem to say that you have
a Linux PC acting as a NATing gateway, but the cable modem already acts as
a NATing gateway from what I can tell, so I'm really at a loss for why
you need your PC's NATing.

I.e. from what I understand you have the following setup:



10.X.X.X local NATed network
|
|
+-- laptops
|
internet --> modem -->--+ |
| |
| |
+-- PC gateway --+
| |
| |
+--- workstations
|
|
|
192.X.X.X second NATed network


[ here I presume that your PC's NAT uses 192.X.X.X, but the actual
range of addresses doesn't matter. ]

I'm not sure if the gateway has a 10.X.X.X address as well on the first
network (probably), and it seems that your 2 local networks (the
10.X.X.X and then 192.X.X.X) are actually physically shared, which is
asking for trouble.

Please tell us which part of the above is wrong,


Stefan