I've set up a network segment on a VLAN on our office router. The gateway IP for the block on the router can be pinged from the outside world fine. Other numbers from the block can be put on machines plugged into the port on the switch and work for all purposes in going to the outside world, but when you try to ping them from the outside world traffic is stopped at the router. The addresses are static, world-reachable and are not behind NAT. I assume the problem is in an access list on the gateway router, but I tried opening up the access list, and even removing it completely, to no avail.