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 ...