Switching Hub Ports

Unlike a repeater hub, in which all ports must operate at the same speed, a switching hub provides ports that operate independently. A hub with switched ports can support 10-Mbps operation on one port, and 100-Mbps operation on another port of the same hub.

Let's consider the case of a switched port on a central hub that is attached to a link segment that connects to a repeater hub. Both hubs are equipped with Auto-Negotiation. The repeater hub, in turn, connects to several computers. In this case, the two hubs would use the Auto-Negotiation protocol on the link that connects them, and would negotiate for the highest common denominator of capabilities that can be supported on that link.

If any computer connected to the repeater hub is equipped with an interface that supports only 10BASE-T, then the repeater hub will operate all ports in 10BASE-T mode, and will also negotiate 10BASE-T operation with the switched port on the central hub. Later, when all machines on the repeater hub are capable of operating at 100BASE-TX, for example, the repeater hub will negotiate a 100BASE-TX link with the central switching hub.

Quick Reference Guide to Auto-Negotiation - 09 SEP 95

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