单项选择题
A. HSRP well-known physical MAC address
B. Vendor code
C. HSRP router number
D. HSRP group number
E. HSRP well-known virtual MAC address
单项选择题 WhichtypeofschemedescribesthedefaultoperationofGatewayLoadBalancingProtocol（GLBP）？（）
单项选择题 Which one of the statements below correctly describes the Virtual Router Redundancy Protocol （VRRP）， which is being used in the Company network to provide redundancy？（）
单项选择题 HSRP has been configured between two Company devices. What kind of message does an HSRP configured router send out every 3 seconds？（）