Switching

Question 1

What determines which switch will become the Root Bridge?

Answer 1

Bridge with the lowest Bridge ID.

Question 2

What makes up the bridge ID?

Answer 2

The Bridge Priority 0 - 61440 (increments of 4096) + System ID Extension (VLAN Number) + MAC Address

The Lowest Bridge ID becomes the root bridge.

Question 3

What command can be used to automatically set a switch as the root bridge?

Answer 3

spanning-tree vlan [vlan] root [primary | secondary]

Question 4

What command is used to change the bridge priority?

Answer 4

#spanning-tree vlan [vlan] priority
(set in increments of 4096)

Question 5

What command(s) can be used to find the root bridge?

Answer 5

show spanning-tree root

show spanning-tree vlan [vlan]

Question 6

How is the Root Path Cost calculated?

Answer 6

Cumulative cost of all links to get to the root

Question 7

If there is a tie in Root Patch Cost how is the root port determined?

Answer 7

Choose lowest upstream BID

Choose lowest upstream Port ID

Question 8

How are designated ports determined?

Answer 8

Lowest Root Path cost
Lowest Bridge ID
Lowest Port ID

Question 9

What is the status of a port that is not a root port or a designated port?

Answer 9

Any port that is not a root port or a designated port is blocked.

Question 10

What does a switch do with traffic received on a blocked port?

Answer 10

BPDU’s are received all other traffic is discarded.

Question 11

What command(s) can be used to change a port’s cost?

Answer 11

#spanning-tree [vlan] cost
#bandwidth [bps]

Question 12

What command can be used to modify the Port ID?

Answer 12

spanning-tree vlan [vlan] port-priority