Boardband & Internal IP conflict

[visor]

I got problem when boardband Internet provider's IP fall into the same range with my Internal network's IP.
For example, a user use boardband connect to Internet with IP address 10.0.0.10. And my office has a PC with IP address 10.190.0.10. In this case, boardband user canNOT ping / use tightvnc connect to office pc. However, if user's boardband IP is 192.0.0.10. This boardband user can ping & access to office pc without problem.

Does anybody know the reason why? I am afraid I will force to resign if I cannot give my management a good answer on this. Please kindly help. Thanks.

 

[MaxPipeline]

The answer to your question is most likely in the subnet mask. If your clients are using a subnet mask of 255.0.0.0 (which is the default for class A subnets which the 10.x.x.x network is a part of) then your clients PC will think that any destinations within 10.x.x.x network will be on the their local LAN. That is if client IP is 10.x.x.x with subnet mask 255.0.0.0 then when that PC tries to goto 10.190.0.10 it only looks on it's local LAN segment and never even attempts to pass this out through the WAN. One possible fix would be to make sure that the client PC has a subnet mask of 255.255.255.0 and an IP address of 10.X.X.Y in which X.X is anything other than 190.0. Or simply change the office network to something else like the 192.168.x.x network.

 

[bcastner]

I would agree absolutely with MaxPipeline's analysis of the issue, if it were not for the fact that a broadband ISP is not going to issue 10.x.x.x public IPs.

Now "if user's boardband IP is 192.0.0.10" is a public IP, but I suspect you meant 192.168.x.x

The only thing I can think of is that a VPN is being used, and in that case the private IPs can conflict. The only thing you can do is to:

. Try for your office a different network subnet from those available under LANA rules:

10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255

. Be very restrictive with your local LAN subnet mask, as MaxPipeline suggested. There is something wrong with your subnet mask if 10.190.0.1 and 10.0.0.1 are seen as being in the same network segment.

 

[Frankenherder]

I agree with some of the above.
Subnets sound similar.

Your ISP should give you a live IP address and not a private one. 10.X.X.X and 192.X.X.X is non routable on the internet. Sounds like they are cheap and a Mickey mouse operation!.

If they will not give you a live IP address, change your internal subnet if it is possible. Make sure your router is doing NAT as well. That would be the easiest way to ensure your subnet's are different.

 

[visor]

Thanks all, Any way I can add a static route blind to network card (but not an IP cause it is dynamic)? My internal network is behind NAT firewall which external address is a real one. I am thinking if I can add a static route to client pc may able to solve the problem. However, if ISP's IP is dynamic, I cannot blind the static route to specific IP. Thanks again.

 

[adlantic]

I have found that if your ISP has a 192.168.0.1 type of NAT sub going on that you can change your gateway on the router to 192.168.2.1, and the conflict goes away.