you should see an option in the modem (the 6100 that is) to set it to RFC 1483 transparent bridging. this should get you going there: »Verizon Online DSL FAQ
»How do I use a router with the Westell 6100?
then all the 6100 should be doing is acting as a "dumb modem".
after this, plug the cable from your modem into the "Cable" port on the back of your gateway unit.
i'm assuming you already did all of the above.
a user manual i found: »ipland.com.ua/modules/pages/doc/···land.pdf
go to page 7, then when it starts talking about connection type, do the following instead:
set it to RFC 2684 routed mode, and put all your static ip details into the router's config page.
report back if you still cannot make it work, or need more help.