Spanning Tree Protocol: RSTP Link Types

RSTP keeps track of port types, ports can either be an Edge or Non-Edge port.

Edge Ports immediately become forwarding after coming up, these ports still send BPDUs but they do not expect to receive any.  Should that port receive BPDUs it will revert to a Non-Edge port and start operating as a common RSTP port.  Unfortunately there is no real reliable way for the switch to automatically detect whether the port is an Edge or Non-Edge port….the default port type is always Non-Edge.

RSTP recognizes two link types:

  1. Point to point link: this is a link that connects RSTP to only one other RSTP switch
  2. Shared Link: This is a link that connects RSTP to two or more RSTP switches.

Most of the time these will be point to point links since modern switches operate in full duplex, this will allow RSTP to define it as a point to point port type, and ports that connect to hubs will only operate in half duplex where the switch will assume shared link port type.  If duplex is not a valid method for your specific implementation, you can configure the port type using the spanning-tree link-type {point-to-point | shared} command



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