Comptia Security Plus Mock Test Q38

A router has a single Ethernet connection to a switch. In the router configuration, the Ethernet interface has three sub-interfaces, each configured with ACLs applied to them and 802.1q trunks. Which of the following is MOST likely the reason for the sub-interfaces?

A.
The network uses the subnet of 255.255.255.128.
B. The switch has several VLANs configured on it.
C. The sub-interfaces are configured for VoIP traffic.
D. The sub-interfaces each implement quality of service.

Correct Answer: B
Section: Network Security

Explanation:
A subinterface is a division of one physical interface into multiple logical interfaces. Routers commonly employ subinterfaces for a variety of purposes, most common of these are for routing traffic between VLANs. Also, IEEE 802.1Q is the networking standard that supports virtual LANs (VLANs) on an Ethernet network.

Incorrect Answers:
A, C, D: Subnets, VoIP, and QoS do not make use of this standard.

References:
http://en.wikipedia.org/wiki/Subinterface
http://en.wikipedia.org/wiki/IEEE_802.1Q