Switching

  • 1.  RSTP BPDU max age

     
    Posted 01-24-2021 14:42
    Hello everyone.

    https://www.juniper.net/documentation/en_US/junos/topics/topic-map/spanning-tree-configuring-rstp.html

    The Juniper documentation above states:
    "RSTP responds to changes within the timeframe of three hello BPDUs (bridge protocol data units), or 6 seconds"

    I take this to mean that the RSTP BPDU's default max age is 6 seconds. However, I see that the max age in the RSTP BPDU shown  below is 20 seconds.

    19:39:16.083654 In 02:05:86:71:4e:02 > 01:80:c2:00:00:00, 802.3, length 39: LLC, dsap STP (0x42) Individual, ssap STP (0x42) Command, ctrl 0x03: STP 802.1w, Rapid STP, Flags
    [Learn, Forward], bridge-id 8000.02:05:86:71:4e:02.81ea, length 43
    message-age 0.00s, max-age 20.00s, hello-time 2.00s, forwarding-delay 15.00s
    root-id 8000.02:05:86:71:4e:02, root-pathcost 0, port-role Designated

    Why is the max-age set to 20 seconds when it should be 6 seconds?

    Thanks,
    Deepak