Network Address Translation Using the OfficeConnect Remote 840

This chapter contains information on address translation using the OfficeConnect Remote 840. It is comprised of the following sections:

• "Selecting Address Translation"

• "Configuring the PAT Default Address"

• "Configuring Static PAT Port Entries"

• "Configuring NAT"

• "Monitoring"

You must have a Remote Site Profile already defined to set up address translation for this remote site.

1 .   From the OfficeConnect Remote 840 Manager "home page," select Configuration > Remote Sites > IP Advanced Modify.

2 .   Select the defined site profile and press the Modify button.

3 .   You will then need to advance through the screens by pressing the Next button until you reach the IP Advanced Modify screen:

4 .   Under Address Translation, select Port Address Translation (PAT), Network Address Translation (NAT), or None (if you are not using address translation).

If you selected PAT, you must enter the default IP address that will be used. Next you will click either Static TCP or Static UDP to select the Port Table type to be managed.

If you selected NAT, click either Dynamic or Static for the IP Address Table to be managed.

When PAT is enabled, the default PAT address can be configured. 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 PAT default address.

Press the Modify button to set the address.

Press the Static Transmission Control Protocol (TCP) or Static User Data Protocol (UDP) button to access the static port tables.

• Static TCP - Press this button to access the static PAT TCP table (above). Using this table, you can map public TCP ports to private IP address / TCP port pairs.

  This is useful for controlling access to the LAN by remote users. For example, an entry containing public TCP port 80, the IP address of a web server on your LAN, and the private TCP port 80 allows controlled access to the web server but not the rest of your LAN. (For a list of assigned port numbers, see RFC-1700, Assigned Numbers document which is available from the Internet.)

• Static UDP - Press this button to access the static PAT UDP table (above). Using this table, you can map public UDP ports to private IP address / UDP port pairs. This is useful for controlling access to the LAN by remote users. (For a list of assigned port numbers, see RFC-1700, Assigned Numbers document which is available from the Internet.)

After Static Port Entries have been configured, return to the IP Advanced Modify screen and press the Modify button for the changes to take effect.

When NAT is configured, static mappings and/or dynamic pools of addresses must be configured. Static assignments permanently map a private address to a public address. Dynamic pools consist of a start IP address, number of addresses in the pool, and a mask to be used for Routing Information Protocol (RIP) messages if the public addresses are to be advertised. Multiple pools can be assigned and static assignments may exist within a pool range.

• Dynamic - Press this button to Add, Delete, or Modify the fields in the Dynamic NAT table:

• Static - Press this button to Add, Delete, or Modify the fields in the Static NAT table:

After Static Port Entries have been configured, return to the IP Advanced Modify screen and press the Modify button for the changes to take effect.

If PAT is used, the active port mappings are shown in the Monitor > Networks > NAT/PAT > Port Assignments screen. Only those mappings for the specified Remote Site will be displayed. This screen shows the active port mappings for both TCP and UDP connections. Each entry consists of the public and the private ports, the remote address and port number, and the value of the inactivity timer.

For both NAT and PAT, the active address mappings are shown in the Monitor > Networks > NAT/PAT > Mapped Addresses screen. Only those mapping for the specified Remote Site will be displayed. This screen shows the active private addresses, the associated public address, and the number of active TCP and UDP connections. When PAT is configured, each entry will have the same public address.

For more information on these monitoring screens, see "Monitoring the OfficeConnect Remote 840" in Chapter 11.