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What ports are on the root bridge of a spanning tree?
One switch is the STP root bridge. All switch ports that connect a link between two switches are either a root port (RP), a designated port (DP), or a blocked port (BP). After link failure the spanning tree algorithm computes and spans new least-cost tree.
How is the root bridge election in spanning tree?
The root bridge is selected by manually configuring its bridge priority to a low value. 32768 is the default value out of a range from 0 to 61440. If all switches in a single spanning tree have the same bridge priority, the switch with the lowest MAC address will become the root bridge.
What is root bridge and root port?
The Root Port is the port on the Bridge (Switch) with the least Spanning Tree Path Cost from the switch to the Root Bridge. A Designated Port is the port on a Local Area Network (LAN) segment with the least Spanning Tree Path Cost to the Root Bridge (Root Switch).
How many root bridges are allowed in a network?
Explanation: You should have only one root bridge per network.
What determines root port?
Root Port selection is based on the port having lowest cost to the Root Bridge (CAT1). When this BPDU receive by any other switch it will add its own port cost (according to the above mentioned value). So if BPDU receive by a Fast Ethernet port (100 Mbps) it will calculate path cost to root as 19 (0+19).
How is the root designated port chosen in spanning tree?
When a switch boot or spanning tree is enabled on a switch, the switch ports pass into blocking state 20 seconds before going into listening state (I read it on Internet but not the case after testing it on Cisco packet tracer) The root bridge election and the root designated port are chosen during the listening state
Which is the lowest bridge in spanning tree?
Root Bridge – The root bridge is the bridge with lowest Bridge I’d. All the decisions like which ports are the root ports (the port with best path to the root bridge) are made from the perspective of root bridge. Path cost – A switch may encounter one or more switch in the path to the root bridge.
When does a switch become a root bridge?
As all the switches have default priority therefore there is a tie on the basis of priority. Now, the switch with the lowest Mac address will become a root bridge. Here, switch A will become the root bridge as it has the lowest Mac address. Therefore, the ports of switch A will be in forwarding state i.e designated port.
Which is the designated port for the root bridge?
Thus port Gi0/1 of Switch B will be selected as the Designated Port for the segment between Switch B and Switch C as Switch B advertised lowest Bridge ID on to the Segment. All ports of the Root Bridge are Designated Ports and any port that is not a Root Port or a Designated Port becomes the Blocking Port and is blocked to prevent loops.