Chapter 5 Configuring Twice NAT (ASA 8.3 and Later)

Guidelines and Limitations

IPv6 Guidelines

•Supports IPv6.

•For routed mode, you can also translate between IPv4 and IPv6.

•For transparent mode, translating between IPv4 and IPv6 networks is not supported. Translating between two IPv6 networks, or between two IPv4 networks is supported.

•For transparent mode, a PAT pool is not supported for IPv6.

•For static NAT, you can specify an IPv6 subnet up to /64. Larger subnets are not supported.

•When using FTP with NAT46, when an IPv4 FTP client connects to an IPv6 FTP server, the client must use either the extended passive mode (EPSV) or extended port mode (EPRT); PASV and PORT commands are not supported with IPv6.

Additional Guidelines

•You cannot configure FTP destination port translation when the source IP address is a subnet (or any other application that uses a secondary connection); the FTP data channel establishment does not succeed.

•If you change the NAT configuration, and you do not want to wait for existing translations to time out before the new NAT information is used, you can clear the translation table using the clear xlate command. However, clearing the translation table disconnects all current connections that use translations.

Note If you remove a dynamic NAT or PAT rule, and then add a new rule with mapped addresses that overlap the addresses in the removed rule, then the new rule will not be used until all connections associated with the removed rule time out or are cleared using the clear xlate command. This safeguard ensures that the same address is not assigned to multiple hosts.

•You cannot use an object group with both IPv4 and IPv6 addresses; the object group must include only one type of address.

•When using the any keyword in a NAT rule, the definition of “any” traffic (IPv4 vs. IPv6) depends on the rule. Before the ASA performs NAT on a packet, the packet must be IPv6-to-IPv6 or IPv4-to-IPv4; with this prerequisite, the ASA can determine the value of any in a NAT rule. For example, if you configure a rule from “any” to an IPv6 server, and that server was mapped from an IPv4 address, then any means “any IPv6 traffic.” If you configure a rule from “any” to “any,” and you map the source to the interface IPv4 address, then any means “any IPv4 traffic” because the mapped interface address implies that the destination is also IPv4.

•Objects and object groups used in NAT cannot be undefined; they must include IP addresses.

•You can use the same objects in multiple rules.

•The mapped IP address pool cannot include:

–The mapped interface IP address. If you specify --Any-- interface for the rule, then all interface IP addresses are disallowed. For interface PAT (routed mode only), use the interface name instead of the IP address.

–(Transparent mode) The management IP address.

–(Dynamic NAT) The standby interface IP address when VPN is enabled.

–Existing VPN pool addresses.

Cisco ASA Series Firewall ASDM Configuration Guide

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Cisco Systems ASA 5545-X, ASA 5505, ASA 5555-X, ASA 5585-X, ASA 5580, ASA Services Module manual IPv6 Guidelines
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ASA Services Module, ASA 5555-X, ASA 5545-X, ASA 5585-X, ASA 5580 specifications

Cisco Systems has long been a leader in the field of network security, and its Adaptive Security Appliance (ASA) series is a testament to this expertise. Within the ASA lineup, models such as the ASA 5505, ASA 5580, ASA 5585-X, ASA 5545-X, and ASA 5555-X stand out for their unique features, capabilities, and technological advancements.

The Cisco ASA 5505 is designed for small businesses or branch offices. It provides essential security features such as firewall protection, flexible VPN capabilities, and intrusion prevention. The ASA 5505 supports a user-friendly interface, allowing for straightforward management. Its built-in threat detection and prevention tools provide a layered defense, and with scalability in mind, it can accommodate various expansion options as organizational needs grow.

Moving up the line, the ASA 5580 delivers greater throughput and advanced security features. This model is suited for medium to large enterprises that require robust protection against increasingly sophisticated threats. Its multi-core architecture allows it to manage high volumes of traffic seamlessly while maintaining excellent performance levels. The ASA 5580 also supports application-layer security and customizable access policies, making it highly adaptable to diverse security environments.

The ASA 5585-X further enhances Cisco's security offerings with advanced malware protection and extensive security intelligence capabilities. It incorporates next-generation firewall features, including context-aware security, and supports advanced threat detection technologies. This model is ideal for large enterprises or data centers that prioritize security while ensuring uninterrupted network performance and availability.

For enterprises requiring a balance of performance and security, the ASA 5545-X presents a compelling option. This model features scalable performance metrics, high availability, and integrated advanced threat protection. Coupled with advanced endpoint protection and detailed monitoring capabilities, the ASA 5545-X enables organizations to manage their security posture effectively.

Lastly, the ASA 5555-X blends cutting-edge technologies with strong security infrastructures. It boasts high throughput and the ability to execute deep packet inspections. Its sophisticated architecture supports threat intelligence feeds that provide real-time security updates, making it a powerful tool against modern threats.

Each of these Cisco ASA models brings specific advantages to varied environments. Their integrative capabilities enable businesses to enhance their security postures while benefiting from seamless scalability and management. As cybersecurity threats evolve, these advanced appliances play a vital role in protecting valuable digital assets.
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