D6#sh span vlan 20
VLAN0020
Spanning tree enabled protocol ieee
Root ID Priority 32788
Address aabb.cc00.0800
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32788 (priority 32768 sys-id-ext 20)
Address aabb.cc00.0800
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Et0/3 Desg FWD 100 128.4 P2p
Et1/0 Desg FWD 100 128.5 P2p
Po1 Desg FWD 100 128.65 P2p
D7#sh span vlan 20
VLAN0020
Spanning tree enabled protocol ieee
Root ID Priority 32788
Address aabb.cc00.0800
Cost 200
Port 4 (Ethernet0/3)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32788 (priority 32768 sys-id-ext 20)
Address aabb.cc00.0900
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Et0/3 Root FWD 100 128.4 P2p
Et1/0 Altn BLK 100 128.5 P2p
Po1 Desg FWD 19 128.65 P2p
I'm troubleshooting a spanning-tree issue and would appreciate your insights.
In my topology, I have a Port-Channel configured between two switches. This Port-Channel has a lower path cost than a direct individual link (Ethernet0/3), but STP still chooses the individual link as the Root Port, instead of the Port-Channel(SW D7)
My expectation was that STP would select the Port-Channel due to the lower path cost (or at least due to fewer hops), but that’s not happening.
Why is STP still selecting the higher-cost or longer path link as the Root Port instead of the Port-Channel?
Any thoughts on what could be causing this behavior?
im thinking its maybe a gns3 problem
Thanks in advance!
