Module 1 Lesson 3: STP
Used to prevent layer 2 bridging loops PVST+ default - One STP instance per VLAN - Cisco proprietary Phase I - Root Bridge Election - "root" of the spanning-tree - Election based on BID - Bridge Priority - MAC Address Phase II - Root Port Election - Upstream port closest to root bridge. STP ROOT PORT ELECTION - Upstream port closest to root bridge - Root port election based on - Lowest cumulative cost - Inverse value based on interface bandwidth - Lowest upstream BID - Used to isolate multiple connections to upstream same bridge - Lowest port ID - Lowest port priority - Lowest port number Portfast - Forward through listening and learning phases BPDU Filter - If BPDU is received revert out of portast state BPDU Guard - If BPDU is received shut port down Root Guard - If superior BPDU is received shut port down Uplinkfast - Immediately transition alternate ports to forwarding when root port is lost BackboneFast - Expire max age when inferior BPDU