Define the components of STP.
Root bridge - get elected (lowest bridge ID wins).
Root port - gets elected, as the POC to talk to the root bridge. based on root path cost. cost equates to speed. faster path cost wins.
- Designated port - election is based on 4 things.
- 1. Lowest root bridge ID
- 2. Lowest root path cost to the root bridge
- 3. Lowest sender bridge ID
- 4. Lowest sender port ID
- All root bridge ports are designated ports.
- Root path cost is cumulative. cost field in BPDU is incremented as it passes through the switch.
If computing root path cost manually, increment the cost as the BPDU is received.