It could be but there's no prompt in the instructions for your modem to set up a static IP. Normally you'd set up a static IP & then go on to forward a port but the portforward site usually includes a prompt to set up that static IP.

I've had a look through those instructions & I can't see anywhere to enter your static IP even if you had set one up.

You might be able to find out from Westell's tech support site?
http://www.westell.com/pages/support/dropdown.jsp

Otherwise, someone else on the forum might have more clues?