Cisco CCNA 200-301: Network Security Fundamentals (Part 4/6)

Learn how to verify standard ACLs by generating test traffic, interpreting deny and permit rules, and reviewing show ip access-list counters to confirm intended access.

Ensure connectivity and proper IP/routing before applying extended ACLs; verify reachability across the topology, then test by blocking ICMP, ping, and FTP traffic to validate ACL rules.

Explore the similarities between standard and extended ACLs, including first-match logic, rule order, host and range matching with wildcard masks, and applying ACLs on interfaces in inbound or outbound directions.

Explain the syntax of extended ACLs, using 100–199 numbers to permit or deny traffic by protocol (tcp/udp/icmp) and port or service name, with source and destination addresses.

Apply extended ACL rules on the correct interface in the desired direction (inbound or outbound) using the source and destination, then verify with packet counters.

Configure a named standard access list using the standard ACL syntax, define rules to deny a host, deny a subnet, and permit any, then apply it on the outbound direction.

Explore how network address translation maps private IPs to public addresses, cover NAT variations (including static NAT), review Cisco IOS configuration, and learn troubleshooting steps.

Learn how NAT translates private IP addresses to a public IP to allow internal networks to access the internet, while hiding internal addresses and conserving public addresses.

Practice nat lab setup by configuring static nat and default routes in a gateway-based topology, translating private subnets to a public ip through a border device and isp.

Use pat with the exit interface to map private addresses to one public ip. Compare static versus dynamic ips, define private ranges with acls, and verify translations for multiple hosts.

Explore why network security matters by defining assets, threats, and risks, and explain countermeasures to protect against protocol weaknesses, clear-text traffic, and phishing.

Explore authentication servers like ACS and ICE for device and network access via portal services, authentication, and recording. Learn how ICE and RADIUS enable health checks, profiling, and access control.

Configure authentication using an external TACACS+ server by setting up the client, shared key, and server IP, with a local fallback for login.

Explore how mac flooding attacks flood the switch’s mac table and how port security limits per-port mac addresses to prevent floods, with violation modes such as shutdown, protect, and restrict.

Explore how a DHCP spoofing attack uses wrong IP configuration from an attacker and how DHCP snooping on Cisco switches prevents this by marking ports as trusted or untrusted.

The lecture demonstrates configuring DHCP snooping on a switch, designating a trusted port for the DHCP server, and verifying clients receive IPs from the correct server.