Spanning Tree Protocol: Port Selection

Spanning Tree Protocol determines which ports are put into a forwarding or blocking state.  The combination of ports that are forwarding or blocking for each VLAN creates a loop free broadcast domain.  STP follows a three step process to determine which ports to forward and block:

  1. Elect the Root switch
    • The switch with the lowest bridge ID is elected the root switch
  2. Determine the Root Port
    • The single port on the switch that receives the superior BPDUs from all received BPDUs on all other ports
  3. Determine the Designated Port for each segment
    • When multiple ports are connected on the same segment, this port is the one that forwards the superior BPDU with least RPC onto that segment

rootportselection

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s