How to BGP protocol discovers neighbourship, how does STP builds topology in switching environment, PING is passing from one network segment to the other via a router on a stick but no response is received, what are the functions of stub areas in OSPF protocol, how many LSAs are there in OSPF, how to identify among FD, AD, S, FS in EIGRP protocol, how do we give or perform LOOP testing be it in hardware or software. How does MPLS, VPN, DHCP, STP, RSTP, VLAN, RIP, IGRP, VoIP, IP TELEPHONY, WI-FI etc works