Home » Cisco » 300-115 » Which enhancement to a spanning-tree design prevents unnecessary traffic from crossing the extended LAN segment?
A network engineer is extending a LAN segment between two geographically separated data centers. Which enhancement to a spanning-tree design prevents unnecessary traffic from crossing the extended LAN segment?
A. Modify the spanning-tree priorities to dictate the traffic flow.
B. Create a Layer 3 transit VLAN to segment the traffic between the sites.
C. Use VTP pruning on the trunk interfaces.
D. Configure manual trunk pruning between the two locations.
Answer: C
Explanation:
Pruning unnecessary VLANs from the trunk can be performed with one of two methods:
. Manual pruning of the unnecessary VLAN on the trunk – This is the best method, and it avoids the use of the spanning tree. Instead, the method runs the pruned VLAN on trunks.
. VTP pruning – Avoid this method if the goal is to reduce the number of STP instances. VTP-pruned VLANs on a trunk are still part of the spanning tree. Therefore, VTP-pruned VLANs do not reduce the number of spanning tree port instances.
Since the question asked for the choice that is an enhancement to the STP design, VTP pruning is the best choice.
http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml
