SECTION B: Procedures: Step $7$ Reassign the root bridge

a$.$ It has been determined that the switch selected as the root bridge, by using default values,

is not the best choice. It is necessary to force the "other" switch to become the root switch.

b$.$ In the example output given the root switch by default is Switch $A.$ Switch $B$ is preferred

as the root switch. Go to the console and enter configuration mode if necessary.

c$.$ Determine the parameters that can be configured for the Spanning$-$Tree Protocol by issuing

the following:

Switch $B($config$)$#spanning$-$tree?

d$.$ List the options.

e$.$ Set the priority of the switch that is not root to $\frac{40}{b}ar(96).$

If version $12\mathrm{.}0$ is used, enter the following:

Switch config$)$#spanning$-$tree priority ${4096}_{?}$

Switch config$)$

If version $12\mathrm{.}1$ is used, enter the following:

Switch Bes $B($config$)$#spanning$-$tree vlan $1$ priority $4096$

Switch config$)$ #exit

Step $8$ Display the switch spanning$-$tree table

a$.$ At the Privileged EXEC mode prompt, type the following on Switch $A$ :

Note: Type show spanning$-$tree brief if running version $12\mathrm{.}0$ of the IOS. If running

version $12\mathrm{.}1$ of the IOS, type show spanning$-$tree.

Switch $A$ A Ashow spanning$-$tree brief

b$.$ On Switch $B$ type show spanning$-$tree brief at the Privileged EXEC mode prompt as

follows:

Switch $B$ BHshow spanning$-$tree brief

Examine the output and answer the following questions.

c$.$ Which switch is the root switch?

d$.$ What is the priority of the root switch?

e$.$ Which ports are forwarding on the root switch? f$.$ Which ports are blocking on the root switch?

g$.$ What is the priority of the non$-$root switch?

h$.$ Which ports are forwarding on the non$-$root switch?

i$.$ Which ports are blocking on the non$-$root switch?

j$.$ What is the status of the link light on the blocking port?

What are the steps from blocking to forward states? How can you observe

them?

Step $9$ Verify the running configuration file on the root switch

a$.$ On the switch that was changed to be the root bridge, type show running$-$config at the

Privileged EXEC mode prompt.

b$.$ Is there an entry in the running configuration file that specifies the spanning$-$tree priority of

this router? Spanning$-$Tree Recalculation

Erasing and Reloading the Switch

It is necessary to start with an unconfigured switch. Use of a switch with an existing

configuration may produce unpredictable results. These instructions allow preparation of the

switch prior to performing the lab so previous configuration options do not interfere. The

following is the procedure for clearing out previous configurations and starting with an

unconfigured switch.

Step $1$ Look at the show interface information

a$.$ On both switches, type the command show interface VLAN $1$ at the Privileged EXEC

prompt as follows:

Switch AAtshow interface vlan $1$

b$.$ What is the MAC address of the switch?

Switch BHshow interface vian $1$

c$.$ What is the MAC address of the switch?

d$.$ Which switch should be the root of the spanning$-$tree for VLAN $1?$

Step $2$ Look at the spanning$-$tree table on each switch

a$.$ At the Privileged EXEC mode prompt, type the following on Switch A:

Note: Type show spanning$-$tree brief if running version $12\mathrm{.}0$ of the IOS. If running

version $12\mathrm{.}1$ of the IOS, type just show spanning$-$tree. Different versions of IOS have

different options for this command.

Switch $A$ A Asshow spanning$-$tree brief

b$.$ On Switch $B$ type show spanning$-$tree brief at the Privileged EXEC mode prompt as

follows:

Switch. $B$ ##show spanning$-$tree brief

c$.$ Examine the command output and answer the following questions.

d$.$ Which switch is the root switch?

e$.$ Record the states of the first $12$ interfaces and ports of each switch

Selecting the Root Bridge

Erasing and Reloading the Switch

It is necessary to start with an unconfigured switch. Use of a switch with an existing

configuration may produce unpredictable results. These instructions allow preparation of the

switch prior to performing the lab so previous configuration options do not interfere. The

following is the procedure for clearing out previous configurations and starting with an

unconfigured switch.

$2900$ and $2950$ Series Switches

Enter into the privileged EXEC mode by typing enable.

If prompted for a password, enter class $($if that does not work, ask the instructor$).$

Switch $>$ enable

Remove the VLAN database information file.

Switch#delete flash:vlan.dat

Delete filename $[$vlan$.$dat$]?[$Enter$]$