CCNA_Spanning-tree - SPANNING-TREE PROTOCOL (802.1d): 1....

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SPANNING-TREE PROTOCOL (802.1d): 1. All of the switches in the network broadcast HELLO BPDUs (Bridge Protocol Data Units) to each other declaring themselves to be root-bridge. 2. The switch with the lowest bridge ID is elected root bridge . The 8-byte bridge ID consists of a 2-byte priority setting (default setting = 32768) and a 6-byte MAC address. The lowest priority setting wins the election. If there is a tie, then the lowest MAC address wins the tie-breaker. 3. The root-bridge places all ports into a forwarding state. 4. The root-bridge broadcasts HELLO BPDUs out of all ports. The root-bridge, by default, send these HELLO BPDUs every 2 seconds with a default cost of 0. The HELLO TIME timer can be adjusted to send the HELLO messages at different intervals. 5. The non-root switch are in the listening state and forward the root's HELLO BPDU broadcasts around the network. Every time a BPDU is forwarded, the cost of the BPDU is incremented based upon the port cost which reflects the speed of the port. IEEE specifies the following port costs : 10 Mbps cost = 100 100 Mbps cost = 19 1 Gbps cost = 4 10 Gbps cost = 2 6. Each non-root switch marks the port that received the least cost BPDU as the root port . The root-port of each switch is set to forwarding . In the event of a tie, the following tie-breakers occur (in order):
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CCNA_Spanning-tree - SPANNING-TREE PROTOCOL (802.1d): 1....

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