Configuring Nat - 3Com OfficeConnect 3CP4144 Cli User's Manual

6-10 C 6: M
HAPTER ANUAL

Configuring NAT

S
ETUP
Static NAT port mappings or the NAT default address need to be configured when
an application will initiate a TCP or UDP connection from the public network. If a
public accessible Server resides on a privately addressed LAN, static ports can be
defined for the applications they are running. For example, TCP port 80 for a Web
Server and TCP port 21 for an FTP server can be statically assigned. The NAT
default address can be used with or instead of static port assignments, and is set
to the private address of a workstation on the local LAN. If an incoming IP data
packet is received on a WAN port and there is no existing dynamic or static port
mapping, the packet will be translated using the NAT default address.
Typically, NAT only needs to be enabled or disabled for a remote site connection.
Use the following command to configure NAT in a VC profile:
set vc <vc name> nat enable
As stated in the above overview, it is sometime necessary to configure the
Workstation default address. This field should be set to the private address of a
workstation on the local LAN. If a data packet is received on the WAN port and a
port mapping does not exist, the frame will be translated using the Workstation
default address.
Use the following command to set this field:
set vc <vc name> nat_default_address <ip address>
Static port configurations map a public port to a private IP address/port. Both TCP
and UDP static ports can be defined. Remote sites can have multiple static ports
defined. If static ports and the Workstation Default Address are defined, the static
ports take precedence.
Static ports are defined for TCP and UDP ports with the following commands:
add nat tcp vc <vc name>
public_port <port>
private_address <ip address>
private_port <port>
add nat udp vc <vc name>
public_port <port>
private_address <ip address>
private_port <port>
Note: Typically the private and public port numbers are configured for the same
value (i.e. 21 for an FTP Server). However, you can map multiple public port
numbers to the same private port number. For example, if you want to support a
Web Server on the LAN and be able to manage your OfficeConnect Remote 812
with the Web Browser, you would define 2 static ports for the Web Server (TCP
port 80). Configure your LAN Server with public port 80, private port 80, and the
private address of the LAN Server. Configure yourocr812 manager with public port
8080, private port 80 and the private address equal to the ethernet port IP
address. To access the ocr812 from a Web Browser, type in: public Address:8080.
The value 8080 was chosen for example purposes only, you can use any value
within the port number range (i.e. 81).