Chapter 21: Cisco IOS Threat Defense Features

Firewall Technologies

• Packet Filtering - Access Control Lists (ACLs) are used to restrict traffic to and from certain addresses and port numbers.
• Application Layer Gateway (ALG) - An ALG operates at the application layer and sits between a client and server (example: HTTP proxy).
• Stateful Packet Filtering - Packet filtering with the added capability of tracking session state.

IOS Firewall Features

IOS Firewall

• Permits/denies TCP and UDP traffic
• Maintains a state table
• Dynamically modifies ACLs
• Denial of Service (DoS) mitigation
• Packet inspection

Authentication Proxy

Provides authentication and authorization for services via TACACS+ or RADIUS.

Supported protocols:

• HTTP
• HTTPS
• FTP
• Telnet

IOS Intrusion Prevention System (IPS)

Responds to suspect traffic with one or more actions:

• Drop - Drop the packet
• Block - Blocks origin IP for a specified amount of time
• Reset - Terminates the TCP session
• Alarm - Logs an alarm