I manage the IT for a group of buildings that have CAT5e going between them. The main office has the Internet connection (DSL) modem, connected to a router. The router has a 16 port 10/100 dumb switch off it (switch a). A cable is then ran to each of the other buildings and the cables are connected to switch a.
At one of the other buildings, a Dell optiPlex Gx755 connects to the cable from the main office. When the cable is connected directly to the OptiPlex, the OptiPlex has a 10 mbps connection. If I add a 10/100 linksys dumb switch (switch b), connect the main office CAT5e to it, and use a 5' CAT5e cable from switch b to the OptiPlex, the NIC can't get doesn't get any connection. The DHCP client address is a 169.x.x.x address instead of a 192.x.x.x address. Even if I assign a static address to the OptiPlex while it's connected to switch b it still doesn't connect to the Internet, nor can I ping anything.