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Source NAT Configuration Overview

The main configuration tasks for source NAT are as follows:

Source NAT Pools

For source NAT address pools, specify the following:

Pool Utilization Alarms

When the raise-threshold option is configured for source NAT, an SNMP trap is triggered if the source NAT pool utilization rises above this threshold. If the optional clear-threshold option is configured, an SNMP trap is triggered if the source NAT pool utilization drops below this threshold. If clear-threshold is not configured it is set by default to 80 percent of the raise-threshold value.

Persistent Addresses

By default, port address translation is performed with source NAT. However, an original source address may not be translated to the same IP address for different traffic that originates from the same host. The source NAT address-persistent option ensures that the same IP address is assigned from the source NAT pool to a specific host for multiple concurrent sessions.

Source NAT Rules

Source NAT rules specify two layers of match conditions:

If multiple source NAT rules overlap in the match conditions, the most specific rule is chosen. For example, if rules A and B specify the same source and destination IP addresses, but rule A specifies traffic from zone 1 to zone 2 and rule B specifies traffic from zone 1 to interface ge-0/0/0, rule B is used to perform source NAT. An interface match is considered to be more specific than a zone match, which is more specific than a routing instance match. For more information about rule set matching, see Understanding NAT Rule Sets and Rules.

The actions you can specify for a source NAT rule are:

Source NAT rules are applied to traffic in the first packet that is processed for the flow or in the fast path for the ALG. Source NAT rules are processed after static NAT rules, destination NAT rules, and reverse mapping of static NAT rules and after route and security policy lookup.

Related Topics

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