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networking:stp [2025/12/03 15:52] – [PORT-FAST] v1ctornetworking:stp [2025/12/03 16:11] (current) – [Root Guard] v1ctor
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 When port flaps, switch sends TCN (topology change notification) message, which forces all switches to re-calculate the root switch. This is not very efficient when port towards the client flaps. In order to mitigate that, customer facing port is configured with **spanning-tree portfast**. This port will be always on (forwarding).  When port flaps, switch sends TCN (topology change notification) message, which forces all switches to re-calculate the root switch. This is not very efficient when port towards the client flaps. In order to mitigate that, customer facing port is configured with **spanning-tree portfast**. This port will be always on (forwarding). 
 +
 +==== BPDU Guard ====
 +
 +We should not receive BPDUs on the customer facing ports. There is a feature which sets the port to **err-disabled** state if switch receives a BPDU on that port.
 +
 +==== Root Guard ====
 +
 +Configuration on the Root switch to protect hijacking the Root role. Configured on the ports.
 +
 +==== MSTP ====
 +
 +Instead of sending BPDU for each VLAN, MSTP aggregates VLANs into the instances and send a single BPDU for that group.
 +
 +On Arista, by default MST instance 0 is created and all VLANs belong to that instance.
networking/stp.1764777141.txt.gz · Last modified: by v1ctor