I have four physical switches I use for studying the CCNP SWITCH. While labbing spanning-tree protocol, I noticed an RSTP particular port role in IEEE spanning-tree mode. Note that this is not RSTP. My switches are running in 802.1D, STP.
DLS2#show spanning-tree VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 24577 Address 000d.bdd3.4e80 Cost 19 Port 2 (FastEthernet0/2) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address 0011.bba6.b000 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Fa0/1 Altn BLK 19 128.1 P2p Fa0/2 Root FWD 19 128.2 P2p Fa0/47 Altn BLK 19 128.47 P2p Fa0/48 Altn BLK 19 128.48 P2p DLS2#sh run | i span spanning-tree mode pvst spanning-tree extend system-id
I have redundant links between my switches. I highlighted the text in bold. VLAN 1 is running IEEE STP and you can see F0/1, F0/47, and F0/48 in Altn port role. The switch command spanning-tree mode pvst is shown in the running-config.
The Alternate port role is actually found in RSTP, 802.1W, as you can see in this Cisco document.
I went out to the networking-forum to see if anyone else had this issue and was then lead to the Cisco Support forums.
