port fast,bdpu guard etc

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port fast:

1) RSTP: goes to discarding and learning state change

2) STP goes to listening and learning

3)we can simply move port to forwarding state using port-fast.

4) on access port

5) to configure on trunk port, different command

per interface#spanning-tree portfast

default on every access port in a switch:

conf t#spanning-tree portfast default

verification:

show spanning-tree interface <> portfast

BPDU Guard:

1) BPDU guard is configured along with portfast.

2) when BPDU is received, port goes to err-disable state

3)

configuration:

(config-if)# spanning-tree bpduguard enable

or

globally

(config)# spanning-tree portfast bpduguard default

Root Guard:

configured on downstream interfaces to prevent any other bridge becoming as root.

if superior BPDU is receieved, port goes to root inconsistent state. once inferior BPDU is received, port comes back.

BPDU guard puts interface in err-disable for any BPDU received. Root guard puts interface in root inconsitent state if superior BPDU than root bridge is received.

Loop Guard:

prevent loops on unidirectional links.