nat server
Function
The nat server command defines a mapping table of internal servers so that external users can access internal servers through address and port translation.
The undo nat server command cancels the mapping table.
By default, no mapping table is configured.
Format
nat server protocol { tcp | udp } global { global-address | current-interface | interface interface-type interface-number } global-port [ global-port2 ] inside host-address [ host-address2 ] [ host-port ] [ acl acl-number ] [ description description ]
nat server [ protocol { protocol-number | icmp | tcp | udp } ] global { global-address | current-interface | interface interface-type interface-number } inside host-address [ acl acl-number ] [ description description ]
undo nat server protocol { tcp | udp } global { global-address | current-interface | interface interface-type interface-number } global-port [ global-port2 ] inside host-address [ host-address2 ] [ host-port ]
undo nat server [ protocol { protocol-number | icmp | tcp | udp } ] global { global-address | current-interface | interface interface-type interface-number } inside host-address
Parameters
Parameter |
Description |
Value |
|---|---|---|
protocol |
Indicates the protocol type. |
- |
protocol-number |
Specifies the protocol number. |
The value is an integer that ranges from 1 to 255. |
global |
Configures external information about the NAT server. |
- |
icmp |
Indicates that servers communicate with each other using ICMP. |
- |
tcp |
Indicates that servers communicate with each other using TCP. |
- |
udp |
Indicates that servers communicate with each other using UDP. |
- |
global-address |
Specifies a valid IP address provided for external access. |
The value is in dotted decimal notation. |
inside |
Configures internal information about the NAT server. |
- |
host-address |
Specifies an IP address of the NAT server. |
The value is in dotted decimal notation. |
host-address2 |
Specifies the ending IP address of the private network. |
The value is in dotted decimal notation. |
global-port |
Specifies the external service port number. You can use keywords to replace common port numbers. For example, the FTP port number is 21, so you can use the keyword ftp. If this parameter is not specified, the value of this parameter is 0. That is, any type of service can be provided. |
The value is an integer that ranges from 0 to 65535. |
global-port2 |
Specifies the external service ending port number. You can use keywords to replace common port numbers. For example, the FTP port number is 21, so you can use the keyword ftp. If this parameter is not specified, the value of this parameter is 0. That is, any type of service can be provided. |
The value is an integer that ranges from 0 to 65535. |
host-port |
Specifies the service port number provided by the NAT server. If this parameter is not specified, the value of this parameter is the same as the value of global-port. |
The value is an integer that ranges from 0 to 65535. |
acl acl-number |
Indicates the number of an ACL. |
The value is an integer that ranges from 2000 to 3999. |
description description |
Indicates the NAT description. |
The value is a string of 1 to 255 case-sensitive characters. It can contain spaces. |
current-interface |
Indicates a public address as the current interface address. |
- |
interface interface-type interface-number |
Indicates a public address as the interface address. |
- |
Usage Guidelines
Usage Scenario
You can configure an internal server so that the external network can access the server in an active manner. When a host on the public network sends a connection request to the public address (global-address) of the internal NAT server, the NAT server translates the destination address of the request into a private address (inside-address). The request is then forwarded to the server on the private network.
- This command can only be used on Layer 3 interfaces, except loopback and NULL interfaces.
- If you run the undo nat server command, static mapping entries are not deleted within the aging-time period. To clear static mapping entries, run the reset nat session command.
Precautions
The specified global-port or host-port cannot be used by other applications. Otherwise, the configuration does not take effect.
If you need to map the private address of an internal server into the IP address of the public network interface when configuring this command on the public network interface, you must set the current-interface parameter to specify a global address as the current interface address.
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