add a route for the cable modem web interface interface

I have an Arris 6190 on ETH0. The default address for the arris is 192.168.100.1. ETH0 is setup to as DHCP, so it can get its address from my provider (Comcast). I want/need to access the Web UI for the Arris. How do I create routes, so devices on ETH1 and ETH2 can brouse to 192.168.100.1, which is on ETH0?

BillK