2 Replies Latest reply: May 14, 2019 6:29 PM by Tuan RSS

    Question about RSTP Message age

    Tuan

      Hi Friends!

      I'm currently study about RSTP and i have read that the Root switch will set the message age in BPDU = 0, all down stream switch will increase the message age value by 1, if the message age equal max age, BPDU will be invalid and devices not all switches will know about topology change.

      I made a simple lab below in VIRL:

      Sw1--------G0/1----------Sw2--------------G0/2------------Sw3

      Switch 1 is the root, all switch run RSTP.

      Here's My understand:Switch 1 will send BPDU with Message age = 0 at g0/1.

      My verification:

      Sw1 :

      Port 2 (GigabitEthernet0/1) of VLAN0001 is designated forwarding

      Timers: message age 0, forward delay 0, hold 0

       

      Switch 2 will send BPDU with message age = 1 at f0/2, But...

      Sw2:

      Port 2 (GigabitEthernet0/1) of VLAN0001 is root forwarding

       

      Timers: message age 16, forward delay 0, hold 0

       

       

      Port 3 (GigabitEthernet0/2) of VLAN0001 is designated forwarding

       

      Timers: message age 0, forward delay 0, hold 0

       

      The Msg age in Port 3 is 0, absolutely is wrong. but when i do packet capture it's right: https://imgur.com/a/bLAUNUk

       

      But why Sw2's port 2 (g0/1) has the msg age of 16? Also the information display on Port 3 is incorrect ? Anyone knows why or Virl is having some issue?Thanks...