AIX PPP set-up for Windows dial-up 2

[aixtechuser]

I'm trying to set up PPP on an AIX 4.3.3 RS/6000. I've got PPP installed and I can dial into the machine via a Windows 98 dial-up connection. I can then telnet to the AIX machine and ping (through MS-DOS) the machine. But, I can't telnet or ping any other machine on the network from the Win 98 PC. I can, however, ping and telnet other machines from within the telnet session. The Win 98 PC can access the network from an NT RAS connection and also works with my dial-up ISP.

I've played with some of the /usr/sbin/no settings (like ipforwarding, etc.) with no luck. I can post all the /usr/sbin/no settings (or any other settings for that matter) if it would help.

Any help would be most appreciated!

 

[francs]

What you have is a routing problem. Firstly the modems uses a ppp interface, which is essentially the same as any other interface, eg. ethernet. Since this is 2 different interfaces they should have 2 different subnets. Lets say you have 3 machines. Your dialup win98 machine, the AIX dialup server and a Linux machine you are trying to connect to. The AIX and Linux machines are on the same ethernet network. ipforwarding=1 on AIX machine and it has 2 interfaces, en0 and pp0. When you ping the Linux machine from the Win98 machine the packet is routed to the en0 network and reaches the Linux machine, but it doesn't know where to send the packet destined for the ppp network. It will then send it to it's defined default gateway, which will forward again to it's default gateway and so forth until max hops are reached and the packet is dropped.

You can resolve this in a few ways.
1. Your default gateway should have an entry in it's routing table that specify the AIX machine as the gateway for the ppp network.
2. Make the AIX machine the default gateway for the Linux machine.
3. Add a static route on the Linux machine that specifies the AIX machine as the gateway for the ppp network.

Of all the above solutions no.1 is the best, because you will only have to do this once for all host on that and other networks. 2 and 3 will have to be done for every host. 2 and 3 also doesn't allow for hosts outside the ppp or aix/linux network.

Hope this helps.

 

[aixtechuser]

Thanks, francs! Your analysis was perfect and extremely helpful!

I put a static route in another AIX machine and was able to communicate perfectly from my Win 98 dial up connection.

But, that got me to thinking - why did my Win NT RAS dial up work? Your explanation was again helpful here. I checked the settings of the Win NT RAS set up and found that the IP numbers used were in our main subnet.

So… I thought I could just set my AIX PPP IP interfaces to be in our main subnet and I wouldn't have to change any other machines. But, no luck.

Any thoughts why this didn't work? Does PPP require its own subnet?

At a minimum, I could take your suggestion and add the new PPP subnet to our main router (a cisco 2620).

Again, THANKS for your quick and very helpful response!