I've just tried using two different ethernet switches on my network to replace an 8-port Netgear gigabit ethernet switch, which works fine, but doesn't have enough ports for what I need. Computers are connected to a TP-Link TD-8840T router via a switch. They use DHCP for IP address assignment.

One switch is a TigerSwitch 6924M, which I'd expect to be difficult to set up, since it is second hand and has an advanced configuration menu, which I can't access without a serial port. However, the second switch that I tried is a new TP-Link TL-SF024, which doesn't appear to have any configuration options, so that can't be the problem.

When I say "not working," I mean that although they display that they are connected to a network, they cannot access the internet. For example commands like "ping -c10 google.co.uk" come up with 100% packet loss.

What could be causing the problem and how do I fix it?