PCs with 2 IP addresses

Nathaniel Stitt (nat@netcom.com)
Mon, 30 Oct 1995 17:44:12 -0800


Cu-SeeMe Developers,

There is a problem with using cu-seeme under Windows NT on machines that
have more than one IP address. This situation arises when the PC is
on a LAN and is using RAS to connect to the internet over a SLIP or
PPP connection.

The problem is that cu-seeme will use the first IP address as the one
to send to the remote video server. If the PC is not reachable over
the internet using that address (because the LAN does not have
internet connectivity) then no connection will be established.

One possible solution would be to allow the user to manually specify
which IP address provides internet connectivity.

Another solution would be to enumerate all IP addresses on the current
machine and send them all to the server, however that might require a
change to the protocol.

I consider this a significant problem because this prevents people
who are using Windows NT and RAS from using cu-seeme.

This also brings up an interesting point for TCP/IP programming
in general: A single computer is *not* limited to having a single
active IP address! Software which assumes that there is only
a single address will encounter problems when that assumption is
violated. (I ran into the same problem in my own sofware!)

Nat