Hi chaps,
I am trying to find out what's going on in a network, where I currently have loads of switches, majority of which are running RSTP, but there are still some running PVST+. I came up to this case, which surprises me a bit and I decided to ping you guys for your thoughts... Right, so here is the network:
[switch A] Gi0/1---- Gi1/0/52 [switch B] ----- [switch X] ----- [ROOT]
^RSTP^ ^PVST+^
Here is what I got on Switch A (which is running RSTP):
SwitchA#show spanning-tree details
VLAN0001 is executing the rstp compatible Spanning Tree protocol
Bridge Identifier has priority 32768, sysid 1, address 0022.be78.0d00
Configured hello time 2, max age 20, forward delay 15, transmit hold-count 6
Current root has priority 24577, address 001e.7a0d.91c0
Root port is 1 (GigabitEthernet0/1), cost of root path is 14
Topology change flag set, detected flag not set
Number of topology changes 279036 last change occurred 00:00:21 ago
from GigabitEthernet0/1
Times: hold 1, topology change 35, notification 2
hello 2, max age 20, forward delay 15
Timers: hello 0, topology change 13, notification 0, aging 300
SwitchA#show spanning-tree
VLAN0001
Spanning tree enabled protocol rstp
Root ID Priority 24577
Address 001e.7a0d.91c0
Cost 14
Port 1 (GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0022.be78.0d00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi0/1 Root FWD 4 128.1 P2p Peer(STP)
SwitchA#show spanning-tree interface gigabitEthernet 0/1 detail
Port 1 (GigabitEthernet0/1) of VLAN0001 is root forwarding
Port path cost 4, Port priority 128, Port Identifier 128.1.
Designated root has priority 24577, address 001e.7a0d.91c0
Designated bridge has priority 32769, address 24b6.57c5.5300
Designated port id is 128.52, designated path cost 10
Timers: message age 15, forward delay 0, hold 0
Number of transitions to forwarding state: 1
Link type is point-to-point by default, Peer is STP
BPDU: sent 111, received 4457838
So .. it looks like I have received TCN on ROOT port, which just doesn't sound right (or I am missing something here).
However, when I go on switch B (which is running PVST+) and when I check the STP details, I cannot see any TCNs being generated:
SwitchB#show spanning-tree detail
VLAN0001 is executing the ieee compatible Spanning Tree protocol
Bridge Identifier has priority 32768, sysid 1, address 24b6.57c5.5300
Configured hello time 2, max age 20, forward delay 15
Current root has priority 24577, address 001e.7a0d.91c0
Root port is 50 (GigabitEthernet1/0/50), cost of root path is 10
Topology change flag not set, detected flag not set
Number of topology changes 94 last change occurred 1w4d ago
from GigabitEthernet1/0/52
Times: hold 1, topology change 35, notification 2
hello 2, max age 20, forward delay 15
Timers: hello 0, topology change 0, notification 0, aging 300
SwitchB#show spanning-tree interface gigabitEthernet 1/0/52 detail
Port 52 (GigabitEthernet1/0/52) of VLAN0001 is designated forwarding
Port path cost 4, Port priority 128, Port Identifier 128.52.
Designated root has priority 24577, address 001e.7a0d.91c0
Designated bridge has priority 32769, address 24b6.57c5.5300
Designated port id is 128.52, designated path cost 10
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 1
Link type is point-to-point by default
BPDU: sent 4457811, received 107
I have done debug spanning-tree events on both switches and for almost 1h - I got nothing. However, switchA constantly reports (pretty much every minute) that there has been change in the topology (and I have not received even a single TCN/TCA..)
What do I miss here? :-)
Many thanks in advance!
