Command Reference Guide

3Com Router 5000 Family and Router 6000 Family nat dns-map ● 217
Command Reference
nat dns-map
Purpose Use the nat dns-map command to configure a NAT entry, mapping a domain name
to a triplet of external IP address, port number, and protocol type.
Use the undo nat dns-map command to remove the NAT entry for a domain
name
Syntax nat dns-map domain-name global-addr global-port [ tcp | udp ]
undo nat dns-map domain-name
Parameters domain-name
Valid domain name that can be correctly translated by
external DNS servers.
global-addr
Public IP address that outside hosts can access.
global-port
Service port number that outside hosts can access.
tcp
Sets the transport protocol to TCP.
udp
Sets the transport protocol to UDP.
Default By default, no map entry exists for any domain name.
Example Map a domain name to a triplet of public IP address, port number, and protocol type.
[Router] nat dns-map www.abc.com 202.112.0.1 80 tcp
View This command can be used in the following views:
■ System view
Description You may configure your internal hosts to access internal servers by domain name. In
case your intranet has no DNS server, an external DNS server will be involved to
provide domain name resolution service.
When an internal host attempts to access an internal server by domain name, its DNS
request is first forwarded to an external DNS server where the domain name is
resolved to a public IP address. The NAT server, however, could not identify the
desired internal server with this public IP address only. To allow it to correctly identify
an internal server by domain name, you must create a NAT entry for the domain
name of the internal server. This entry must include a service port number in addition
to the public IP address.
You may create up to 16 NAT entries for domain names.