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High message age when using mixed 802.1d + 802.1w

Hi there,

We are using an mixed environment 802.1d/802.1w and are seeing unusual high message age values on the trunk ports of end switches. This age is hopping between 15 to 20 causing loopguard to kick in.

The core is running 802.1d, the leave switches are running 802.1w

To further investigate the issue I have analyzed vlan 104:

SW1:

Port 1 (GigabitEthernet0/1) of VLAN0104 is root forwarding
   Port path cost 3004, Port priority 128, Port Identifier 128.1.
   Designated root has priority 8192, address 000b.xxxx.xxxx
   Designated bridge has priority 16384, address 000b.xxxx.xxxx
   Designated port id is 128.129, designated path cost 3
   Timers: message age 15, forward delay 0, hold 0
   Number of transitions to forwarding state: 1390
   Link type is point-to-point by default, Peer is STP
   Bpdu filter is enabled internally
   Loop guard is enabled by default on the port
   BPDU: sent 3924, received 11482485

The output above is of the end switch. In terms of hop count, this switch is 2 hops away (cost 4(1gb) + cost 3(2gb) + uplinkfast 3000=3007) from the root of vlan 104:

VLAN0104
  Spanning tree enabled protocol rstp
  Root ID    Priority    8192
             Address     000b.xxxx.xxxx
             Cost        3007
             Port        1 (GigabitEthernet0/1)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

The following output is the switch in between the core and SW1 which is displaying the correct message age being received in the BPDU send from the core:

SpanningTree enabled for vlan = 104

                BPDU-related parameters
port spanning tree                   enabled
state                                forwarding
port_id                              0x8301
port number                          0x301
path cost                            3
message age (port/VLAN)              1(20)   <--------------

If I understand the message age correctly, this should be 2 or 3 instead of 15+ as this is being refered to as a hop count value.

We have another switch connected to the same core switch, which is of the same type, 3560, and is running in pvst+, the same version the core switch is running. This switch is showing the correct message age for the same vlan 104:

SW2:

Port 49 (GigabitEthernet0/1) of VLAN0104 is blocking
   Port path cost 3004, Port priority 128, Port Identifier 128.49.
   Designated root has priority 8192, address 000b.xxxx.xxxx
   Designated bridge has priority 16384, address 000b.xxxx.xxxx
   Designated port id is 128.193, designated path cost 3
   Timers: message age 2, forward delay 0, hold 0  <---
   Number of transitions to forwarding state: 0
   Link type is point-to-point by default
   Loop guard is enabled on the port
   BPDU: sent 2, received 45424265

Could the high message age be related to the fact we are mixing RSTP +  802.1d?

The reason we would like to know the cause for this is we are also seeing many loopguard blocking/unblocking events on the end switches which have rstp enabled, and are experiencing a very high message age timer.

Thanks!

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