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internet not working - think subnet mask on dsl router wrong

Posted on 2004-03-22
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Last Modified: 2013-11-30
we have 32ips assigned with swbell w/ our dsl package and we subnetted it with 255.255.255.240 on all our pc's, which made 2 networks

network A usable ips: 70.70.70.193 - 70.70.70.206
network B usable ips: 70.70.70.209 - 70.70.70.222

70.70.70.200 and 70.70.70.209 are t1 routers which connect our two offices/networks.

70.70.70.202 is our netopia cayman dsl router in network A, which provides the internet for both networkA & B.

70.70.70.193 is our win2k server, and it hosts our exchange server, dns server, everything.  the workstations are setup in office/network A as follows an example of 1 workstation:

IP: 70.70.70.194
Subnet: 255.255.255.240
gateway 70.70.70.202
dns1: 70.70.70.193


our internet has died and i belive it is the cause of our dsl router

the dsl router ip which was updated from swbell is 70.70.70.202 w/ subnet mask of 255.255.255.248

am i correct in that the subnet mask is wrong and should be 255.255.255.240 on the dsl router?

please advise, and i will have it changed hopefully and see if this solves the problem.

thanks
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Question by:unisold
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by:MaB
ID: 10655716
Hi unisold,
You shouldn't have the same IP on the dsl routers external and internal interface. (.202) They must differ since they are on different networks. The subnet .248 from your ISP is for the external interface and that's no problem.

BR MaB.
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by:unisold
ID: 10655754
once i get remote administratio enabled somehow i'll check, but i think the 70.70.70.202 is the internal interface, and the external interface has some other IP which is like the WAN ip or something.

if what i just said is the case, then it would need .240 right?

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MaB earned 125 total points
ID: 10655787
Yes, that's right. If it has .248 it's interpreted as on another network since the subnet defines how many computers that are allowed in the network.  
MaB
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by:unisold
ID: 10655900
ok, ya the more my memory visualizes how the remote administration appeared, the more i remember LAN ip = 70.70.70.202 w/ it needing .240, and the WAN ip was some 60.60.60.x something with a different subnet mask.

i'll let you know what we find out, thanks for the support

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Expert Comment

by:PennGwyn
ID: 10660822
You havn't describe any way for anything to connect DSL to LAN B at all.

The .248 net mask, though, does break the ability of the DSL router to talk to the T1 at .200, which I assume is the breakage you're experiencing.

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