What are two ways to force the selection of a root bridge in a network that is running the 802.1D
protocol? (Choose two.)
A.
spanning tree vlan all root
B.
spanning-tree vlan vlan-id priority 65535
C.
spanning-tree vlan vlan-id root
D.
spanning-tree vlan vlan-id priority 0
E.
spanning-tree vlan vlan-id force root
Explanation:
The IEEE 802.1 standard (STP) is used to create a loop-free Layer 2 network. This protocol uses
the bridge ID (a field inside BPDU packets) to elect root bridge. It is 8 bytes in length. The first two
bytes are the Bridge Priority, which is an integer in the range of 0 – 65, 535 (default is 32, 768).
The last six bytes are a MAC address supplied by the switch.
In STP, lower bridge ID values are preferred. To compare two bridge IDs, the priority is compared
first. If two bridges have equal priority, then the MAC addresses are compared. For example, if
switch A (MAC=0600.0000.1111) and B (MAC=0600.0000.2222) both have a priority of 10, then
switch A will be selected as the root bridge because it has lower MAC.