Cisco CCNA Routing and Switching ICND2 200-101 Official Cert Guide

RSTP Port States

RSTP added one new port state compared to STP (discarding) using it as a replacement for the STP port states of disabled and blocking. You might think that after you configure a switch to use RSTP rather than STP, instead of seeing ports in a blocking state, you would now see the discarding state. However, the Cisco Catalyst switch output basically ignores the new term discarding, continuing to use the old term blocking instead.

For example, scan back to the most recent RSTP example (Example B-4), to the line for SW3’s port G0/2. Then look for the column with heading STS, which refers to the status or state. The output shows G0/2 is listed as BLK, or blocking. In theory, because SW3 uses RSTP, the port state ought to be discarding, ...