3Com Switch 8800 Advanced Software V5 Configuration Guide

NAT Configuration Task List 989
scalability. The special protocols supported by the Switch 8800s include: Internet
control message protocol (ICMP), domain name system (DNS), Internet locator
service (ILS), and NetBIOS over TCP/IP (NBT).
NAT multiple-instance
This feature allows users from different MPLS VPNs to access external networks
through the same outbound interface. It also allows them to have the same
internal network address. The process works as follows:
When an MPLS VPN user communicates with an external network, NAT replaces
its internal IP address and port number with the NAT gateway’s external IP address
and port number. It also records the relevant MPLS VPN information, such as the
protocol type and router distinguisher (RD for short). When the response packet
arrives, the NAT gateway then restores the external IP address and port number to
the internal IP address and port number. Additionally, the NAT gateway can
identify the users who access the external network. Besides NAT, NAPT also
supports multiple-instance.
The multiple-instance feature can also apply to internal servers so that external
users can access an internal host of an MPLS VPN. For example, in MPLS VPN1, the
host that provides WWW service has an internal address 10.110.1.1. The host can
use 202.110.10.20 as an external IP address so that the Internet users can access
the WWW service in MPLS VPN1 through this external address.
NAT Configuration
Task List
Follow the following steps to configure NAT:
To do... Use the command... Remarks
Enter system view system-view -
Define an address pool nat address-group
group-number start-address
end-address
Optional
Not necessary when the
switch has been configured
with Easy IP.
Configure address translation Refer to “Configuring
Address Translation” on page
990.
Required
Configure an internal server Refer to “Configuring Internal
Server” on page 991.
Optional
Enable NAT application layer
gateway
nat alg { all | dns | ftp | ils |
nbt }
Optional
Enabled by default
Currently, the NAT ALG
supports only standard ports
for DNS, FTP, ILS, and NBT.
Configure the binding Refer to “Configuring the
Binding” on page 992
Required
Configure NAT log Refer to “Configuring NAT
Log” on page 993
Optional
Disabled by default
Configure connection-limit Refer to “Configuring
Connection-limit” on page
996
Optional
Disabled by default