TCN headers and fields

Since PVST+ is based on STP, and Rapid-PVST+ is based on RSTP, TCN BPDUs are sent only in PVST+ and not in Rapid-PVST+ mode.

For introductory information about STP BPDUs, see the section TCN BPDUs.

Table 1. Extreme PVST+ TCN BPDU headers/fields
Header/field

Standard IEEE STP TCN BPDU

(64B with padding)

PVST+ untagged TCN BPDU

(64B with padding)

PVST+ tagged TCN BPDU

(68B with padding)

MAC SA 6B 6B 6B
MAC DA 0180C2.000000 (6B) 030408.000700 (6B) 030408.000700 ((6B)
Length 2B 2B -
Type - - 81 00 (2B)
802.1q tag - - 4B
SSAP 42 03 AA 03 AA 03
DSAP 42 AA AA
Cisco OUI - 02 04 08 02 04 08
PVST PID - 01 0B 01 0B
LLC 3B 8B 8B
SNAP 4B Entire BPDU with type = TCN 35B Entire BPDU with type = TCN 35B
Table 2. Cisco PVST TCN BPDU headers/fields
Header/field

Standard IEEE STP TCN BPDU

(64B padded)

PVST untagged TCN BPDU

(64B padded)

PVST tagged TCN BPDU

(68B padded)

MAC SA 6B 6B 6B
MAC DA 0180C2.000000 (6B) 01000C.CCCCCD (6B) 01000C.CCCCCD (6B)
Length 2B 2B -
Type - - 81 00 (2B)
802.1q tag - - 4B
SSAP 42 03 AA 03 AA 03
DSAP 42 AA AA
Cisco OUI - 00 00 0C 00 00 0C
PVST PID - 01 0B 01 0B
LLC 3B 8B 8B
SNAP - Yes Yes
IEEE TCN BPDU INFO 4B Entire BPDU with type = TCN 35B Entire BPDU with type = TCN 35B