Symptom
When running the debug spann bpdu command BPDUs with a message age of greater than 20 are seen in the STP data field:
.Dec 15 12:23:54.602: STP: VLAN0001 rx BPDU: config protocol = rstp, packet from TenGigabitEthernet1/3 , linktype IEEE_SPANNING , enctype 2, encsize 17
.Dec 15 12:23:54.602: STP: enc 01 80 C2 00 00 00 F0 78 16 F4 4B 02 00 27 42 42 03
.Dec 15 12:23:54.602: STP: Data 000002020F6001F44E05076B00000000CA8001F07816F44B00803A3200140002000F00
.Dec 15 12:23:54.603: STP: VLAN0001 Te1/3:0000 02 02 0F 60
SW5#01F44E05076B00 000000CA 8001F07816F44B00 803A 3200 1400 0200 0F00
.Dec 15 12:23:54.603: RST(1): Te1/3 superior msg
.Dec 15 12:23:54.603: RSTP(1): Te1/3 rcvd info remaining 1
.Dec 15 12:23:54.603: %SPANTREE-5-TOPOTRAP: Topology Change Trap for vlan 1
.Dec 15 12:23:54.603: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 1: New Root Port is TenGigabitEthernet1/3. New Root Mac Address is xxxx.xxxx.xxxx
0x3200 = 50 Message Age
0x1400 = 20 Max Age
Conditions
Layer 2 switched network running RSTP or Rapid-PVST+.
Further Problem Description
It seems there is no max value on how high the message age can go. In the production enviroment BPDUs with a message age of way above 200 are seen. It is worth mentioning that the production enviroment runs Rapid-PVST+ but the behavior is also seen in RSTP.
This bug is a exact replica of CSCux57150 which is reported for Cat4k.
