Win2k: Changing netmask address?? - This question isnt easy!

[Darksamie]

I have an internal network behind a dialup adapter with a bank of 64 IP addresses. In order to get tehse IP addresses working locally on the other PCs, I need to change the netmask address of the dialup adapter from 255.255.255.255 which si the default to 255.255.254.0 which will allow me to trace to my IP addresses from outside the subnet.

Please note that I am *not* trying to change the netmask of the NIC, this is easily done.

 

[CTR]

So your server is dialing up and using that connection to route traffic for the /26 network you described?

255.255.254.0 is a really odd netmask for this case -- a dialup connection is point-to-point. Why would you need to change the netmask in order to trace into your network? I don't think it is possible to override the dialup server's netmask setting as a client anyway. Perhaps there is some other issue keeping your routing from working. What is an active IP address in your range that I can test?

Can you post the routing table on your NT server (with the dialup connection active).

 

[LordOfAll]

Just a suggestion here but...

why dont you take one step back and tell us the equipment you have and what software you are using and we can probably help you. CTR has some good points. Also , if you will, tell us how much experience you have. I hate given a blow by blow to a vet or totally confusing a novice.

 

[Darksamie]

Here is the equipment that we currently have....

5 computers, all running Windows 2000 Professional. The connection is through a PSTN modem, with standard 10Mbps NICS in every computer. The connection has a dedicated IP address which is 139.*.*.* and then we have a bank of addressed 203.52.*.* to address each machine (the bank is 64 IPs).

On calling my ISP, they said that the problems we were having (I cant trace to the machine IPs (203.52.*.*) from outside the network) were caused because the subnet mask was wrong. The current default subnet mask is 255.255.255.255 and they said I had to change it to 255.255.254.0

I consider myself fairly good with networking, so you can launch anything at me.

 

[spirites]

I don't know why you don't just use a proxy/NAT program which makes things really easy, but in your case you will need to play with the "route" command. Open up a msdos prompt and type "route" and enter to get the commands and instructions. You will probably have to make a batch file and run that each time the pc is booted up to change the routing table manually. I don't know too much about this stuff, but that would be a good start. Good luck...

 

[CTR]

Microsoft dial-up adapters always show 255.255.255.255 as their netmask because that's just how they do it. You can't change it.

Can your machine that is dialing up access the Internet, and can you traceroute to it from outside the network? When you traceroute to a host on your LAN,where does it die?

Also, has your ISP specifically told you that they have added a route to your LAN network in their equipment?

 

[LordOfAll]

OK I'm not familiar with PSTN but here goes.

Lets just for examples sake say your modems addy is 139.0.0.1. with a netmask of 255.255.255.255 only that IP is in the subnet. With a subnet of 255.255.254.0 you get the range of 139.0.0.1 to 139.0.1.255. How exactly is that supposed to help you reach your block of 64 at 203.54.*.* ? Answer, it won't. What are you using to route on your end? What I mean is does the modem connect to a w2k machine with 2 nics, or do you have the modem plugged into a router, or is the modem plugged right into a switch or hub?

This is a RIP propagation problem.

 

[Darksamie]

Ok.....here goes....this is all the information I have on it.

The IP address for the modem is 139.130.213.169

The bank of internal IPs we have is 203.52.56.128 (64 IPs)

The IP address of the modem (139.130.*.*) is traceable, but the other IP of that machine (203.52.56.131 is the NIC address) is not.

The subnet mask I was told to use for the modem is 255.255.254.0 (for 139.130.213.169)

The subnet mask I was told to use for the NICs is 255.255.255.192 (for 203.52.56.*)

The setup we have is an internal modem in one machine using Internet Connection Sharing built into Win2k. There are four other machines on the network.

Incidently, if you do a trace to 203.52.56.131, it will timeout at lon-22, this is the router over the road from us and is also out Gateway address for the modem IP.

Let me know if you need anything more....

 

[LordOfAll]

I did a tracert to your internal IPs and it stopped at your modem not the lon-22 router. So now the problem lies with your internal routing. This sounds like an ICS problem. What specifically can't you do? Get out to the I net, get in from the I net?

 

[Darksamie]

Hmmm, it seems I can trace to all the internal IPs I have except the one that is the host as well.

The problem is, I cant get in from the I net. All the PCs there can browse etc, but when I go to access one of the PCs directly, it won't work.

 

[LordOfAll]

Your joking right? You really want to have open access to your entire LAN from the Internet? You do realise that that is almost no security at all, right?

ICS is not a routing program per se, it's made to do NAT.

 

[Darksamie]

Unfortunately I have no choice in the matter. It is something that I have been told to do, if only I can work out how to do it.

Any ideas?

 

[LordOfAll]

Well sorry mate but you have gone past my experience. Since I would never do this the way you are asking to I don't have any experience. Also Im an NT 4 guy. In NT 4 I would just make a routing table to do what you want, but Im not sure if this is possible in w2k. I think ICS is your problem. It is designed to block the internal ports of your LAN. So you either need to open the ports or map them all to internal IPs.