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

Configure IP addresses, bring interfaces up, and set routing so three subnets communicate, then apply access rules to restrict traffic as a standard ACL lab prerequisite.

Learn to configure standard ACLs to deny or permit traffic by matching a single host or a network with wildcard masks, and verify the rules on the command line interface.

Explore how wildcard masks control which bits to match in access control lists, calculate from subnet masks, and apply to match hosts, networks, or ranges while understanding default deny.

Learn how to write ACL statements, decide on the transit interface for deployment, and distinguish standard versus extended ACL by focusing on source, destination, and the denied traffic.

configure a standard access control list to filter traffic by source with permit and deny rules, using a wildcard mask or host syntax, and apply the acl to enforce reachability.

Apply access control lists to the correct interface and direction, placing them nearest to the destination to ensure intended traffic is filtered and unintended traffic is not denied.

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.

Learn how applying an ACL on the wrong interface and direction can fail to block undesired traffic, because inbound and outbound flows alter return traffic.

Learn how to write standard access-list statements to match specific traffic using IP addresses and wildcard masks, with examples on permit and deny, and verification.

Learn to interpret standard access-list statements, calculate wildcard and subnet masks, and determine IP ranges that match permits or denies.

Use extended ACLs to filter traffic by source and destination IP, protocol category, and specific services or ports, enabling precise permit or deny rules beyond what standard ACLs offer.

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.

Explore extended ACLs and how to apply them, deciding where traffic flows between networks, whether to split rules, and how to define source, destination, and service, with DMZ considerations.

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.

Configure extended access control lists by ordering rules, applying on the outer interface, specifying source and destination, protocol category, and ports, denying dhcp, dns, and icmp while permitting the rest.

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.

Learn to craft extended ACLs with one-line statements that deny or permit traffic by source, destination, and protocol, using wildcard masks, slash notation, and port ranges.

Learn how named access control lists replace numbers in standard and extended ACLs, with case-sensitive names that ease editing and identification, and explore the first-match rule and editing challenges.

Learn how named access-list syntax uses ip access list with a name, choosing standard or extended types, including host, any, and wildcard options, with sequence-based rules and editing.

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.

Learn how to configure named extended ACLs with the IP access list extended syntax, including protocol, source, destination, and service constraints, and verify and apply them for outbound traffic.

Learn to edit named and standard ACLs using the new syntax. Master inserting and removing lines with sequence numbers, including placing statements between numbers and using default multiples of 10.

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.

Explore why networks use globally unique public IPs, how IPv4 exhaustion drove private networks and address translation, and how translating private to public addresses enables internet connectivity and route summarization.

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.

Understand static NAT, dynamic NAT, and borderless translation, plus NAT overload via port numbers, comparing 1:1 mappings to many-host access.

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.

Explore static nat configuration to translate private addresses to public ones using inside and outside interfaces. Verify translations with show ip nat translations and clear ip nat translations.

Configure port address translation (PAT) overload to map many private addresses to a single IP, using an ACL and a public IP pool, and verify with show ip nat translations.

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.

Define the three core goals of network security—confidentiality, integrity, and availability—explaining encryption to protect data in transit, hash-based integrity checks, and defending against denial-of-service attacks to keep networks up.

Explore physical, internal, and external threats to networks and learn practical mitigations using physical security, access controls, backups, data loss prevention, and firewall-based defenses.

Identify and classify organizational assets, including information, databases, software, and documentation. Assess asset value, confidentiality, and replacement cost to determine appropriate security measures.

Classify countermeasures into administrative, physical, and technical controls, then apply policies, security training, audits, and network access controls like firewalls and guest access to reduce risk.

Explain the AAA framework—authentication, authorization, and accounting—and its application to device administration and network access, with examples of user credentials, access rights, and activity auditing.

A firewall sits between trusted inside networks and untrusted internet, inspecting traffic and enforcing policies to allow only approved data, while dmz hosts services to limit exposure.

Explore intrusion prevention systems (IPS) that detect and block malicious traffic in real time through deep packet inspection, protecting networks from unauthorized access and exploits.

Explore how virtual private networks connect customer sites over preexisting transport networks via provider edge devices, using point-to-point or point-to-multipoint configurations, IP-based VPNs over Internet to reduce costs.

Explore next generation firewalls and their advanced features, including application visibility control, identity-based access control, user-based rules for devices, url filtering against cloud or network databases, and intrusion prevention systems.

Learn how authentication verifies user identities, authorization defines what resources a user can access, and accounting tracks actions across devices and networks.

Explore the aaa components: supplicant, authenticator, and authentication, and see how end devices gain network access through authenticators, with authentication services storing credentials and enforcing authorization by policy.

Centralize authentication, authorization, and accounting by using external AAA servers, avoiding scalable issues of local databases as devices forward login requests to TACACS+ servers.

Explore AAA protocols such as TACACS and RADIUS, and how authentication, authorization, and accounting govern secure network access and device administration.

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.

Learn how to authenticate device users using local username and password or external authentication services, with backup local options, and configure privilege levels and enable passwords.

Learn to configure local database authentication on a device, create local user accounts, and set a primary authentication method with local as fallback, then test logins.

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

Explore layer two security options to mitigate internal LAN threats and learn how switches and firewalls work together to protect end users and guest access.

Learn why disabling unused ports on switches is essential for security. Identify unused ports and ensure they are not available to connect to the network, preventing unauthorized access.

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.

Configure port security on access ports with a two MAC limit and sticky dynamic binding, then verify violations and MAC table entries using traffic and shutdown, restrict, and protect modes.

Configure and verify native VLAN on 802.1Q trunks, manage untagged frames, and align native VLANs across switches to prevent mismatches and ensure communication.

Learn to use the Cisco discovery protocol (cdp), a Cisco proprietary tool, to gather hardware, topology, and neighbor information for troubleshooting Cisco networks, using commands like show cdp neighbors.

Learn how the link layer discovery protocol (LLDP) shares neighbor device details, such as capabilities, descriptions, and IP addresses, and how to enable and verify it on interfaces.

Explore the vulnerabilities of CDP and LLDP, which reveal device and network information, and learn practical mitigations by disabling CDP and LLDP on untrusted interfaces using global or interface-level commands.

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.

Explore DHCP starvation attacks and their impact on IP address pools, showing how attackers spoof MAC addresses to exhaust leases and how port security mitigates by limiting learned MACs.

Explore how dynamic arp inspection prevents arp spoofing attacks by building ip-to-mac bindings through dhcp snooping or manual entries, then validating requests and dropping mismatches on untrusted ports.