单项选择题
A. 79xx IP phones do not automatically mark voice packets with non-zero DSCP values.
B. 79xx IP phones do not mark protocol packets such as DHCP, DNS, or TFTP with non-zero DSCP values.
C. 79xx IP phones do not mark voice packets with optimal DSCP values.
D. 79xx IP phones use a custom protocol to communicate CDP information to the switch.
单项选择题 VLAN Tagging, also known as Frame Tagging, is a method developed by Cisco to help identify packets travelling through trunk links. When an Ethernet frame traverses a trunk link, a special VLAN tag is added to the frame and sent across the trunk link .How does ERS use the VLAN tag?（）
单项选择题 When is the site-to-site remote access model appropriate? （）
单项选择题 Which of these statements best describes VPLS?（）