I wonder if someone could clarify somethign for me please regarding STP root guard.
My study material and this Cisco document (http://www.cisco.com/warp/public/473/74.html) states that a port configured with root guard will place that port into root inconsistent state if a superior BPDU is received on the port. Ok no problem here.
It then states that when the switch sending the superior BPDU ceases to send them, then the port with root guard configured will come out of root inconsistent state and transition to listening, learning and then forwarding mode.
What I don't understand is under what condition will the switch sending the superior BPDU ceasse to send them?
Will it except that a switch which has a higher BID (the administratively configured root bridge)is the route bridge and stop sending it's own BPDU's?
Best Regards & TIA,
The new switch will NOT accept the current root switch's bpdu, because the current root switch's bpdu is worse than its own bpdu (the current root switch has a higher bridge ID value).
After all, this is the preliminary condition of the scenario:
"If a port ..... receives a SUPERIOR bpdu from a new switch added to the network"
As I mentioned, this is the normal behavior of STP. The same process happens when the root selection occurs initially:
1. The switch with the superior bpdu continues sending its own bpdus, because it does not hear better bpdus than its own.
2. All other switches stop sending their own bpdus, because they can hear a better bpdu.
This is the root selection process itself.