500gx, how can I create a virtual interface?

[bartgrefte]

Hi!

I've got an 500G Deluxe with Oleg's firmware 1.9.2.7-7e and a cablemodem from Arris.

Now here's the thing: I'd like to be able to open my cablemodems webinterface but that's not possible while it's online, at least that's what I though.
Someone mentioned that it is possible when a virtual interface is created in the router with an IP-address that's in the range of the cable modem's (internal) IP-address.

ifconfig eth0:0 192.168.100.2/24 (where eth0 is the wan interface) should do the trick, although I haven't tried it.
Plus, it should be placed in the startup script, which is /etc/init.d/S95custom-user-startup in OpenWRT, but that script doesn't exist or it's somewhere else in Oleg's firmware.
Anyone know where I can find it?

With regards,

Bart Grefte

[Tamadite]

I wonder if it should not be easier to route that specific IP address directly to the WAN port.

[bartgrefte]

Don't think that will work, since the ip-address of the modem is in a different range than my network.
Modem: 192.168.100.1
Network: 192.168.1.*

Only works when the computer, or router with virtual interface, is in the same range, from what I've read from other people wanting able to do this.