3Com 3C840 manual 2APPENDIX C Address Translation Tutorial

C-2APPENDIX C: ADDRESS TRANSLATION TUTORIAL

Network Address With NAT, a pool of public addresses is configured and dynamically

Translation (NAT) mapped to a private workstation address when accesses are made through the gateway to a public network. The public-to-private address mapping remains active until the privately-addressed workstation stops accessing the public network. The public address is then returned to the available pool of addresses.

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, the number of addresses in the pool, and a mask to be used for RIP messages if the public addresses are to be advertised. Multiple pool and static assignments may exist within a pool range.

NAT Example Your remote site administrator or ISP provides a pool of addresses for your local LAN.

If there are enough addresses for each machine and your OfficeConnect Remote 840, you do not need to use NAT. Simply assign each machine an address from the pool. If the number of machines is greater than the number of available addresses, use NAT. As with PAT, you make up a private IP network for the LAN and assign an IP address from that network to each workstation and the OfficeConnect Remote 840 (LAN IP address). RIP (if enabled) must be set to “listen only” so the OfficeConnect Remote 840 will learn routing information from the WAN but will not broadcast the private network information. Doing this