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Difference between Root Port and Designated Port

  • Last Updated : 04 Oct, 2021

Root Port: 

A Root Port is a single selected port that has the lowest Path Cost to the Root Bridge. The Root Port on the Bridge (Switch) is the port with the lowest Spanning Tree Path Cost from the switch to the Root Bridge.

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  • The root port is a direct link to the single root bridge or we can say it has the shortest path to the root bridge.
  • If more than one connection connects to the root bridge, a port cost is calculated by evaluating the bandwidth of each link.

Designated Port:

The designated port has the lowest spanning-tree path cost on a specific Local Area Network(LAN). The path cost depends on the speed of the bridge port interface. The cost of each port on either side of the segment and the total cost computed by STP for that port to go back to the root bridge are used to choose designated ports on a per-segment basis.

  • A bridge may have numerous Designated Ports (Switch).
  • A Root Bridge’s (Root Switch’s) ports are all Designated Ports, and there is no Root Port on a Root Bridge (Root Switch).

Let’s see the difference between Root Port and Designated Port:

Root PortDesignated Port
A single selected port on a switch, other than root switch.The designated port is the port on every switch(root/non-root switch).
Least path cost from a non-root bridge to reach the root bridge.Lowest STP cost on a particular local area network (LAN) segment to the root bridge.
Only one root port is presents on a non-root switch.There may be multiple designated ports presents on a switch(root/non-root).
No root ports are present on a root switch.All ports of root switch are designated ports.
One end If root port, opposite will be designated port (never be blocking port). One end is the designated port, opposite will be either the designated port or non-designated port.
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