We have a new ISP. It is a /29 block of static IPs through Time Warner Cable Business Class. Our old service was a T1 with a /28 block of static addresses. (We have drastically reduced the number of devices needing to connect so when we ordered the new service we cut it to a /29 block.)
The old service worked exactly as expected. I could connect any device to the service, configure one of the unused IPs using subnet mask 255.255.255.240 and it worked fine.
Thus far we have been unable to get the new service to work properly. When we connect a laptop to the modem and configure one of the new IPs with a subnet mask of 255.255.255.248, the laptop works correctly, as expected.
However, when we connect any other device they do not work. We've tried a DVR surveillance system, a firewall and a router. When connected to the new service we can't ping them. We know they are responding to the ICMP requests when received because they respond when connected to the old service. If we take a properly configured laptop connected to one of the Ethernet ports on the new modem we can ping the other devices that are also connected to the modem. So, again, the devices are responding. But we can't ping them from the Internet side.
TWCBC insists the connection is working and their only guarantee is that the connection is good to the modem. They are not responsible for any devices connected to the modem. They claim they don't block any ports on the Business Class Service.
We are going to make a decision tomorrow about whether to just terminate the new service and keep our old service.