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Problems With connectivity with ISP through 851 Router

                  HI everybody,

I have quite a strange problem at my work, i was supposed to setup a connection on one of our remote locations at work. We have bought a business ADSL connection with 1 static IP address from our ISP at that location, but for some reason i cannot get it to work with my 851 router. I must say that I have setup the same/similar connection on many other locations but this one simply does not want to work. FIrst things first.

When I connect mz laptop to the modem that I recieved from the ISP and enter the static IP address and gateway into the laptop's NIC card i have all connectivity, i can reach the internet etc.....

When i connect an other laptop and do the same thing, i have no connectivity i cannot reach the gateway and nothing.

I have also tried to connect 2 same (New) 851 routers to the ISP's modem and the also don't work. Both of them have only basic configurations with the WAN interface (Fastethernet 4) given the static IP Address and Subnet Mask. and a default static route to the ISP Gateway. I have called my ISP several times and ask them to clear their ARP, they did that several times and right after that they can see my device and it's IP address and they map it correctly, but when i ping the gateway it's not working. Also when i do the "show arp" command on the router i cannot see ISP's device MAC, i tried this with both routers. When i do the arp -a command from the laptop that is working i can see their MAC (Gateway,s MAC).

I also tried to setup vlan 1 on the router with the static IP address recieved from the ISP and connected the modem a port on the router witch is in vlan 1 and still nothing can't be seen.

I also tried to map ISP's MAC address manually on the router but still nothing. Also tried to upgrade the IOS on the routers again clear configuration and did a basic new conf from scratch....nothing.

I really don't know what to do more..... something like this never happened before. Has anyone any idea what this could be and any experience on this.

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