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Bronze

STP questions

 

Hi everybody

 

I hope you are doing fine. 

 

R1 e1--------f1/1 Sw2

 

R1 is router, e1 routed port, sw2 layer 2 switch,

sw2 is the root of vlan 1 ( no other switch so it makes sense)

 

sw2#show spanning-tree vlan 1

 VLAN1 is executing the ieee compatible Spanning Tree protocol
  Bridge Identifier has priority 32768, address c001.0714.0000
  Configured hello time 2, max age 20, forward delay 15
  We are the root of the spanning tree
  Topology change flag set, detected flag set
  Number of topology changes 1 last change occurred 00:00:34 ago
          from FastEthernet1/1
  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

 Port 42 (FastEthernet1/1) of VLAN1 is forwarding
   Port path cost 19, Port priority 128, Port Identifier 128.42.
   Designated root has priority 32768, address c001.0714.0000
   Designated bridge has priority 32768, address c001.0714.0000
   Designated port id is 128.42, designated path cost 0
   Timers: message age 0, forward delay 0, hold 0
   Number of transitions to forwarding state: 1
   BPDU: sent 32, received 0

 

Consider the highlighted text above.

 

Topology change is 35 , notification 2

Sw2 never sends or receive 35 topology change or 2 notifications but yet they always show up

is there any reason ?

 

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1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Hello,Actualy this is not a

Hello,

Actualy this is not a counter. This is the time TC flag is being held:

"The TC bit is set by the root for a period of max_age + forward_delay seconds, which is 20+15=35 seconds by default."

http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/12013-17.html

HTH

Niko

1 REPLY
Cisco Employee

Hello,Actualy this is not a

Hello,

Actualy this is not a counter. This is the time TC flag is being held:

"The TC bit is set by the root for a period of max_age + forward_delay seconds, which is 20+15=35 seconds by default."

http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/12013-17.html

HTH

Niko

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