350-030 CCIE Voice Written Online Class

Demo Question 10.

Network topology exhibit Configuration exhibit. There are customer complaints about voice quality between IP Phones. What could be the potential problem? (Assume that all switchports are configured to trust DSCP and that the WAN link is less than 768 kbps).

A. None of the other alternatives apply.
B. It is NOT possible to configure multiple DSCP matches in one statement under 'class-map'. So, the packets that are marked as DSCP=5 by IP phones are not going through priority queue. Instead, it is going through 'default queue '. So, IP phone packets are getting delayed. Thus, it caused the voice quality problem.
C. It is possible to configure only TWO DSCP matches in one statement under 'class-map'. Due to this invalid config the packets that are marked as DSCP=5 by IP phones are not going through priority queue. Instead, it is going through 'default queue '. So, IP phone packets are getting delayed. Thus, it caused the voice quality problem.
D. It is possible to configure multiple DSCP matches in one statement under a given class-map. Since the "voice-qos" class is matching three different DSCP values, they are all being assigned to the same "priority" queue, where they are processed in a FIFO manner, which is causing excessive delays on the slow-speed WAN link.


Display Answer

Answer: D

Explanation: