Optional STP Features

STP has been around for more than 30 years, first being used even before the IEEE took over the development of Ethernet standards from Xerox and other vendors. The IEEE first standardized STP as IEEE 802.1D back in the 1980s. Cisco switches today still use STP. And other than changes to the default cost values, the description of STP in this chapter so far works like the original STP as created all those years ago.

Even with such an amazingly long life, STP has gone through several changes over these decades, some small, some large. For instance, Cisco added proprietary features to make improvements to STP. In some cases, the IEEE added these same improvements, or something like them, to later IEEE standards, whether as ...

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