Cisco IOS Security: Guide to Implement a Basic Firewall

Configure a basic firewall with Cisco IOS ACLs, including standard and extended, numbered and named. Learn ACL processing order—sequential matching and implicit deny—and apply ACLs to interfaces inbound or outbound.

Create a named standard access list with ip access-list, deny the 103 network using a wildcard, and apply it on serial 1/0 with ip access-group.

Learn to edit a standard ip access-list by adjusting sequence numbers and masks without deleting it, respect line priority, and save or back up configurations before applying changes.

Learn to use host and any with wildcard masks to define access lists, match ip ranges, and control traffic with exact host matches and all addresses.

Explore extended access lists to control traffic by source, destination, protocol, ports, and time ranges, including dynamic and named options, with practical Cisco IOS examples.

Apply an extended access-list to block inbound ICMP echo requests on the interface closest to the source, denying ICMP while permitting other traffic, using numbered and named ACLs.

Implement an extended access list to drop inbound ftp traffic from any source to any destination on the internet-facing interface, and add a time-range for office time.

Explain reflexive access lists that use a state table to permit outbound traffic and return traffic, with dynamic 300-second entries enabling ICMP replies.

Demonstrates policy-based routing with an access list that permits ICMP, uses a route map to apply to an interface, and drops other traffic via a discard interface, tested with ping.

Enable ip access-list logging to capture traffic matched by the list and send aggregated logs to a server, using thresholds and intervals to balance load.

Learn to drop packets with IP options on Cisco IOS security by using extended access lists and policy maps to match and deny option-laden traffic on specific interfaces.

Secure Cisco IOS access by configuring enable and enable secret passwords, enabling service password-encryption, and authenticating line console and line vty logins with usernames or local passwords.

Configure Cisco devices to use a RADIUS or TAC X server for AAA, enabling authentication, authorization, and accounting, with a local fallback and remote login profile.

Examine Cisco IOS privilege levels and AAA authentication and authorization with a local username database, showing how users gain or are denied access to configuration and show commands.

Assign commands to administrators with different privilege levels by navigating exec and configuration modes, using commands like configure terminal, interface, and ip address to enforce access.

Use an access-list to restrict VTY (telnet) access to inside the enterprise, authenticate with a username/password, and apply an inbound access-group on VTY lines to block DMZ and internet access.

Learn to enforce network-aware login options on Cisco IOS by differentiating enterprise networks, limiting password attempts to three before a temporary lockout, and tuning block durations. Configure logging of successes and failures, quiet mode, and access lists to permit admins from trusted networks while blocking others.

learn how to implement role-based cli with views in Cisco IOS by assigning privilege levels, creating parser view for interface and debugger admins, and a supervisor view for combined access.

Create and use class maps to classify traffic, decide match all versus match any, nest maps inside policy maps or zone based firewall, and verify with show commands.

Create a class-map with match-any to classify downloads by protocol, URL, mime types, and file extensions, using or logic for movie and music traffic, and understand the default match-any behavior.

Define and apply class maps with policy maps to block downloads on interfaces, demonstrating nesting of policy maps, per-service policies, and the importance of class order.

Explore CBAC concepts with intercept and watch modes, and learn how IP inspect applies to TCAP and UDP connections. Configure thresholds, timeouts, and access lists to control incomplete connections.

Explore how TCAP connections use a three-way handshake, how half-open connections cause a sand attack, and how TCAP intercept acts as a transparent proxy to protect the server.

Define a dmz server subnet, create an extended ip access-list for those servers, configure ip tcap intercept with timeouts and thresholds, and verify with debug and test connections.

Configure context-based access lists (seabag) on the untrusted interface to inspect outbound traffic, enforce an inspection profile, enable alerts, and apply inbound and outbound deny rules for unsolicited traffic.

Learn how Cisco's IP traffic export enables span-like monitoring and remote span by exporting bidirectional traffic from serial interfaces to a server, with ACL filtering and one-in-100 sampling.

Learn to implement a zone-based firewall configuration for DMZ, internet, and enterprise zones using class maps and policy maps to inspect and control traffic.

Explore Cisco's zone-based firewall, using zones like enterprise, DMZ, and internet, to define zone pairs, policy maps, and class maps that inspect and govern return traffic.

Master zone-based firewall configuration in Cisco IOS and validate traffic flows by testing internet and DMZ access, using ICMP reachability tests and HTTP (port 80) connections to verify allowed paths.

Configure a three-zone zone-based firewall for enterprise, DMZ, and internet, defining zone pairs, class maps, and policy maps to inspect bidirectional traffic between zones.

Extend policy maps with zone-based firewall policing to inspect traffic from internet to DMZ, limit sessions, and cap incomplete connections per minute and per host.