dhcp relay?

I have a cable modem/router which have a built-in dhcp server. I have a
route PC with multiple network cards connecting to the cable modem and
other PCs connect to the route PC.

How to let other PCs get the dhcp address from the cable modem?

Thanks.

Nick wrote:

> I have a cable modem/router which have a built-in dhcp server. I have a
> route PC with multiple network cards connecting to the cable modem and
> other PCs connect to the route PC.
>
> How to let other PCs get the dhcp address from the cable modem?
>

I think you dont want that ! (If I'm wrong, I peg your pardon - then you
should google about dhcp relays or bridging)


each networkcard should represent one subnet. Otherwise your route-PC will
not know on which networkcard it should send a certain network-packet.

Your dhcp-server on the cable-modem only gives ip's for one subnet.

So what you want is maybe something like this:

A) the cable-modem and all your PC's are connected via a switch. Then all
PC's will get their adress inside one subnet from the cable-modem

B) each PC is in its own subnet and the route-PC masquerades the
connections. Then you could setup a dhcp-server on the route-PC or just
assign static adresses.

peter



--
peter pilsl
pilsl_usenet@goldfisch.at
http://www.goldfisch.at

Nick <nbdy9@hotmail.com.nospam> wrote:
> I have a cable modem/router which have a built-in dhcp server. I have a
> route PC with multiple network cards connecting to the cable modem and
> other PCs connect to the route PC.
>
> How to let other PCs get the dhcp address from the cable modem?

Firstly, I would suggest disabling the DHCP on the modem, and moving it
to your Linux router. More control that way, and better flexibility.

If you really wanted DHCP to work across broadcast domains (across
routers), then you can install dhcp-relay on the Linux router. Under
Debian, you can use the dhcp3-relay package. Otherwise, it may come in
your dhcp server package.

--
Cameron Kerr
cameron.kerr@paradise.net.nz : http://nzgeeks.org/cameron/
Empowered by Perl!

Nick <nbdy9@hotmail.com.nospam> wrote in message news:<bu42mq$dls$1@news3.bu.edu>...
> I have a cable modem/router which have a built-in dhcp server. I have a
> route PC with multiple network cards connecting to the cable modem and
> other PCs connect to the route PC.
>
> How to let other PCs get the dhcp address from the cable modem?

The network interface connecting to the cable modem should be running
dhcp client, for example: dhcpcd eth0 (assuming eth0 is to the cable
modem). The second interface should be running dhcp server, for
example: dhcpd -i eth1, serving a local subnet. Other PCs are then
dhcp clients to this local subnet.

see: http://ide-cf.info-for.us/firewall.html

>
> Thanks.

Looks the moderm dhcp server can issue an public Internet IP, that's why
I want to do relay...

Cameron Kerr wrote:
> Nick <nbdy9@hotmail.com.nospam> wrote:
>
>>I have a cable modem/router which have a built-in dhcp server. I have a
>>route PC with multiple network cards connecting to the cable modem and
>>other PCs connect to the route PC.
>>
>>How to let other PCs get the dhcp address from the cable modem?
>
>
> Firstly, I would suggest disabling the DHCP on the modem, and moving it
> to your Linux router. More control that way, and better flexibility.
>
> If you really wanted DHCP to work across broadcast domains (across
> routers), then you can install dhcp-relay on the Linux router. Under
> Debian, you can use the dhcp3-relay package. Otherwise, it may come in
> your dhcp server package.
>

Nick <nbdy9@hotmail.com.nospam> wrote:
> Looks the moderm dhcp server can issue an public Internet IP, that's why
> I want to do relay...

That doesn't sound right. Do you have bridging turned on? Surely it
should be doing NAT, unless you intend to do NAT on the Linux router.

--
Cameron Kerr
cameron.kerr@paradise.net.nz : http://nzgeeks.org/cameron/
Empowered by Perl!