Hi there. I've got the following task:

I have a 255.255.255.0 network from 192.168.0.1 to 254. The gateway is a linux machine at 192.168.0.1.

It uses a dsl dialup and currently has the following routing:

Code:
# route -n
Ziel            Router          Genmask         Flags Metric Ref    Use Iface
217.0.xxx.xxx   0.0.0.0         255.255.255.255 UH    0      0        0 ppp0
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 eth1
192.168.99.0    0.0.0.0         255.255.255.0   U     0      0        0 eth0
0.0.0.0         217.0.xxx.xxx   0.0.0.0         UG    0      0        0 ppp0
We bought a hardware router, which is meant to replace the linux machine, which has the IP 192.168.0.250.

Now I want to keep the linux machine running and routing, while it uses the new hardware router. I need this, so I don't have to change all the configurations of the clients at once (no DHCP here).

Question: do I have to use two ethernet cards, like in the current state, where eth0 is connected to a DSL modem?
Or can I just happily connect eth1 to the network of the new hardware router and tell the linux machine that it forwardes everything to 192.168.250?

Can you give me a hint? Got iptables installed. Thankyou!