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IP Addressing Issue

Posted on 2014-03-15
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Last Modified: 2014-03-20
I needed to expand device capability on my network. The new scope is 10.0.0.1-10.0.15.254 with subnet mask of 255.255.240.0.

Gateway address is 10.0.0.1. DHCP server (SERVER 2008R2) is 10.0.0.5. Router and server have been updated to new scope with correct subnet mask, etc. I can ping, for example, from 10.0.6.30 to 10.0.0.1 but have no Internet access unless the device has an address of 10.0.0.x.

Devices properly find their IP address reservations. What's wrong here?
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Question by:johncarullo
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by:Santosh Gupta
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which router you are using, plz check if ACL is created for complete IP range.
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Bing CISM / CISSP earned 500 total points
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if all devices do stay on the same large single subnet, it looks like your gateway has an incorrect mask configured.

its current maks seems to be 255.255.255.0, the correct one is 255.255,240.0.

please have a check.
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by:johncarullo
johncarullo earned 0 total points
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Thanks for your help. Problem solved. This facility is a school with a filter sitting between the router and the LAN. There was a typo in the subnet mask on the filter. Instead of 255.255.240.0. The subnet mask was set to 255.255.255.0. It all makes perfect sense now.
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by:Bing CISM / CISSP
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as i speculated, 254 incorrectly became 250.

good to know it has been solved.

BTW, just one more concern on the size of single subnet. the capacity allows more than 4K (255*16) hosts on the same subnet in the same broadcast domain, that's normally not a good practice except you actually have a few hosts online and they do need such a big IP space.

commonly, you need a central router to connect, say 16 subnets, for better performance and security.
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by:johncarullo
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I've requested that this question be closed as follows:

Accepted answer: 500 points for bbao's comment #a39931627
Assisted answer: 0 points for johncarullo's comment #a39931636

for the following reason:

I found a typo in subnet mask
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