IP and port numbers

[Bob Cherry]

At 10:36 AM 5/28/98 -0700, Wen, Shixing wrote:
>Could someone explain how a machine can have more than one ip address? 
>
>Shixing Wen

Many systems have more than one IP for a variety of reasons.  One generally
requires two ethernet controllers if the system is to operate on two
different networks however, a single IP can be used as long as both IPs are
within the same network realm.

Port numbers (sockets) are totally independant from IP addresses.  Your
"services" file defines which services use what ports.  In addition, access
lists (used with router configurations) can determine which
ethernet/internet addresses support which ports.  The Policy Editor may be
able to give you some additional control (Windows95/NT) but I haven't
entered that world yet.

How you configure your system to handle this is dependant upon the OS,
platform, network type and number of network controllers.

Reasons for running multiple IP addresses can include:
Multi-service system (DNS, Web Server, Mail Server, etc.)
Network Router
Network Firewall
Virtual Private Data Network and Internet
etc.

Enjoy!
Bob Cherry
Internet Network Consultant