Network Services such as NAT (Network Address Translation), DHCP (Dynamic Host Configuration Protocol), NTP (Network Time Protocol), SNMP (Simple Network Management Protocol).ACLs (Access Control Lists), Cisco IOS Security Features, AAA (Authentication, Authorization, and Accounting).GRE (Generic Routing Encapsulation), IPSec VPN, DMVPN (Dynamic Multipoint VPN), VPN Troubleshooting.