VTP pruning does not prune extended?

[George-Sl]

According to this fact the answer C is incorrect, and answer D is right,
Am I right??

VTP pruning takes effect several seconds after you enable it. VTP pruning does not prune traffic from VLANs that are pruning-ineligible. VLAN 1 and VLANs 1002 to 1005 are always pruning-ineligible; traffic from these VLANs cannot be pruned. Extended-range VLANs (VLAN IDs higher than 1005) are also pruning-ineligible.

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.

[Mark Malone · Accepted solution]

hmm I think its C because it states what spanning-tree enhancement , manual pruning is not an STP enhancement its manual , its a trick question its states what cant be pruned but it does not tell you your using them or they need to be pruned and they just ask what would you use to prevent unnecessary traffic . either would work but an enhancement i would have thought is not manual changes

its an older question as well as newer VTPv3 supports extended vlans , VTPv1v2 does not even transfer vlans 1002-1005 to be pruned anyway only v3 would

Thats just my opinion on it anyway

[George-Sl]

Even vtp3 does not do pruning for extended part

yeah you right, I was thinking the same thing, the "enhancement" part

[HakanT]

I read this question too, which is causing me quite a headache. Basically, if the requirement is, to extend a VLAN to another site, than it conflicts with the requirement, to prune that VLAN from the trunk. Anyway, I would also prefer D. instead of C., because:

1. If the question would ask for preventing unnecessary traffic only, then C. might be more comfortable than D – IF VTP ist used! Anyway, both would work. But the question gives no hint if VTP is used or not. Moreover it lets me guess, that no VTP is used, if the LAN segment must be extended by the "network engineer" (VTP would do this automatically)

2. If I’m not wrong, only D. would be an enhancement to a STP design, because VTP pruning (C.) does not enhance the STP design, when reading this:

“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.”
https://www.cisco.com/c/en/us/support/docs/lan-switching/vtp/98155-tshoot-vlan.html

3. There is another document, that tells about various enhancements regarding VTPv3. But the only statement regarding STP is an enhancement to MST, which doesn't matter for that question:

"VTP usability has been enhanced [...] to support spanning tree, or more precisely the MST instance, to the VLAN mapping table with IOS"

https://www.cisco.com/c/en/us/products/collateral/switches/catalyst-6500-series-switches/solution_guide_c78_508010.html

But I also found a third document, that gives a little chance to C. ;-)

"Prune any VLAN that you do not need off your trunks. VTP pruning can help, but this kind of plug-and-play feature is not necessary in the core of the network."

https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/10556-16.html#prune_vlans

Anyway, in practice I would choose D. instead of C., as I would not have more information.

But unfortunately we are confronted with on of these annoying test-questions ;-)