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subnetting question

I've got a client that changed the subnet mask of his class C network to 255.255.252.0. It was 255.255.255.0. The address range that we were using was 192.168.253.0 - 192.168.253.254. Now the client is trying to use the 192.168.252.0 - 192.168.255.254 range. This just does'nt look right to me.

Has anyone got any thoughts on it ?

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New Member

Re: subnetting question

The new range is correct, the new mask is 22 bits long. To see the valid subnets you need to subtract the third octets mask from 256, which gives a base number of 4. To see which network the 192.168.253.0 address belongs to divide the third octet by 4, giving 63.25. The network address is therefore 63 x 4 = 252 - the next network would be 252 + 4 = 256. Therefore the valid address ranges are 192.168.252.0 - 192.168.255.255, with the .255 address being the broadcast address for the network.

You need to make sure however that your customer does not already have a 192.168.252.0 with a Class C mask.

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