Firstly, I have no knowledge of hubs, so please keep any advice simple!
I have a UNIX hub, connecting three PCs and would like to know if the hub has NAT translation for incoming packets and if th hub is able to NAT translate packets coming in to a local (internal) LAN address..
Do you mean that your Unix host has 3 LAN connections (interfaces) and acts as a hub ?? If yes, then NAT is available between the interfaces so long as each is defined with a different subnet address. Best Linux example is the use of 'ipchains' for configuring simple NATing rules (IP Masquerade) and configuring your host to act as a router between the subnets. See Linux IP Masquerade HOWTO
If you have a seperate piece of network equipment, i.e. a hub, then I would suspect that the answer is no. You will need to purchase a piece of equipment with NAT capability, i.e. a router.
Leigh
wait i have a question, if you set up a unix box running a firewall and routing, the box has two network interfaces, one is connected to a dsl modem and the other to a 4 port switch, that computer cant do NAT?
True you do not have to run NAT if you are allowing the equipment your communicating with at the end of the dsl link to communicate via the assigned IP addresses of your devices on the 4 port switch. This is not a very secure firewall practice, but is completed by definition of routing (IP forwarding etc)!?
However assuming that you are now talking about an internet connection and unless all of the devices connected to the 4 port switch have a registered IP address, NAT must exist to allow the internal devices IP addresses to be translated to an address recognised (registered) on the internet. This translation may well be performed on your dsl modem (functionality of device dependant). By basic definition of a firewall, NAT is used to mask internal addresses.