How to configure two static IP on one PC(router)?

[selenus]

We get static IP address and its unclear how this need be configured. Small LAN - 6 computers, that connected to 8 Port Switch. Switch connected to router PC(Unix based). That router PC get internet connection via Ethernet
cable (from ISP). This PC router have another static IP address. The question is how to configure (and what configure) this two IP such a way that we can use our
IP address independently from another IP address have this PC router, i.e. we need transfer IP address through this router in both directions, and did not prevented/mix with
another IP.

 

[rkinner]

You need to set up NAT on the UNIX PC Router. You don't say what version of UNIX but IP Filter works on most versions:

http://coombs.anu.edu.au/~avalon/

Ron

 

[selenus]

Hi,
I'll check version of this PC router(this PC router is outside of our LAN, it have also another LAN connected). So this work need be done on that PC router, not on our LAN PCs? Someone adviced that we need configure HOST files, but I'm not sure where. As I suppose, the admin of that PC router have no idea what need be configured, so I need specify him exactly what need be done.

selenus

 

[rkinner]

On the PCs you set up the default gateway to point to the inside IP address of the UNIX PC. That's about all you can do on the PCs. Most of the work has be on the UNIX PC.

The PCs will send packets destined for the Internet to the UNIX PC. The UNIX PC will then use NAT (Network Address Translation) to replace the source address of each packet it gets from the inside with either its own outside IP address or an address from a NAT pool (just a range of legal addresses it is allowed to use) and then send them on to the Internet. It keeps a table of the original source address and port number and the destination address and port number and the substituted address and port number.

When it sees a packet come back from the internet it looks up the incoming packet's destination address and port number in its table and converts the destination address and port number back to the original address and port number.

IP Filter is also a firewall so it can also refuse entry to all but packets to certain ports or only allow packets which have the Established bit set (are in reply to a packet from the inside) but you can tell it to allow all packets and not do the firewall bit.

There is a fairly detailed HOWTO article on that same link that should explain how to set it up. The only information need for basic NAT is the inside IP address and mask, the output IP and mask and the default gateway (to the Internet). All of this your UNIX guy should have already. He just needs to install IP Filter and configure it per the HOWTO.

Ron

 

[selenus]

Thanks a lot.

selenus