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CCNA Security 640-554 Quick Reference by Anthony Sequeira

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Chapter 3. Cisco IOS Firewalls

Firewall Technologies

Firewalls are a key security technology in the modern network infrastructure. This section details their evolution and the technologies that have resulted.

Firewall Fundamentals

The firewall should

• Be resistant to attacks.

• Be the only transit point.

• Enforce the access control policy of the organization.

Static Packet-Filtering Firewalls

These work at Layers 3 and 4, examining packets one at a time and are implemented on a Cisco router using access control lists (ACL).

Advantages of these firewalls include the following:

• Based on simple permit and deny sets

• Low impact on network performance

• Easy to implement

• Supported on most routers

• Initial security at a low network layer

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