Spanning tree understanding of Cisco Packet Tracert

Lab Environment:

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Experimental Purpose:

1. Simple description of Spanning tree.

2. Observe that a switch belongs to the root bridge.

3, observe the switch is not the root bridge, the port is "blocked".

4. Set the port of the server to Spanning-tree Protfast.

5, set the SWITCH1 as the root bridge; Modify the priority of the spanning tree, the lower the number, the higher the priority level.

Operation Steps:

1. Simple description of Spanning tree.

A: The default Cisco switch enables spanning Tree protocol and automatically calculates the root bridge, the disabled port, and so on.

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2. Observe that a switch belongs to the root bridge.

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3, observe the switch is not the root bridge, the port is "blocked".

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4. Set the port (FA0/4) of the server to Spanning-tree Protfast.

Coresw#conf T

Enter configuration commands, one per line. End with cntl/z.

Coresw (config) #int FA0/4

CORESW (config-if) #spanning-tree portfast

%warning:portfast should only is enabled on ports connected to a single

Host. Connecting hubs, concentrators, switches, bridges, etc ... To this

interface when Portfast is enabled, can cause temporary bridging loops.

Use with CAUTION

%portfast have been configured on FASTETHERNET0/4 but would only

The effect when the interface are in a non-trunking mode.

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The reasons for setting up Protfast are as follows:

By default, the switch port, after the switch starts, for STP reasons, the port needs at least 30 seconds before the user can provide data forwarding.

For a

Ports that are connected to the host or server are not necessary for STP calculations, as such ports are not even directly

Forwarding data does not cause loops, and 30 seconds is a long time for hosts or servers that need to deliver data immediately, so such ports can be configured to bypass STP calculations.

5, set the SWITCH1 as the root bridge; Modify the priority of the spanning tree, the lower the number, the higher the priority level.

Switch (config) #spanning-tree VLAN 1 priority 4096

Switch (config) #exit

Switch#show Spanning-tree

VLAN0001

Spanning Tree Enabled Protocol IEEE

Root ID Priority 4097

Address 0090.214B. DA35

This bridge is the root

Hello Time 2 sec Max Age sec Forward Delay sec

Bridge ID Priority 4097 (priority 4096 Sys-id-ext 1)

Address 0090.214B. DA35

Hello Time 2 sec Max Age sec Forward Delay sec

Aging Time 20

Cisco Packet Tracert Spanning tree understanding