General Forums >> Ask A Tech Expert >> Help with subnets
Help with subnets
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Posted 5 months ago Ok here is my question for any networking techies out there. I am in school studying networking and we are working on figureing out subnet mask, my problem the text that we have is very confusing. I am trying to get a better understanding of how you figure the subnet mask and how the math works. If anyone out there can help shed some light on this it would be greatly appreciated. My instructor has sent me some tips and his notes on the subject but I am still pulling what hair I have out.
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680 posts back to top |
| Posted 5 months ago it seems to me the only place anyone wants you to fiqure a subnet by hand is in school. teachers just don't get it when there are better and easier ways to do.it something to do with learning the basics i guess. i use the following. http://www.freewarefiles.com/LanCalculator_program_13205.html i know this doesn't help your school work much, but take it with a grain of salt. i haven't done it by hand since i graduated 5 years ago. |
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175 posts back to top |
| Posted 5 months ago Thanks for the help, I'll check it out. |
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| Posted 4 months ago
Okay I am going to take a shot at this. Keep in mind I am not a teacher but anyway. It all comes down to the subnet mask So when you see 255.255.255.0 it actually means 11111111.11111111.11111111.0 Anything that is a 1 is either part of the network or the subnet. So generally you work backwards. First how many networks do you need? Let's say you need 4 networks 4 = 2 ^ x x = 2 This means you need to borrow 2 bits from hosts 11000000 = 2^7+2^6 =192 decimal Therefore your subnet mask is 255.255.255.192 The broadcast address is always all 1s So that makes 00000001 to 00111111 1 63 Network 1 You can not use the last address because it is all 1 and therefore the broadcast address. I left it there to show the progression. So it would appear in this case 62 host are available per subnet. 01000001 to 01111111 65 to 127 Network 2 10000001 to 10111111 129 to 191 Network 3 11000001 to 11111111 193 to 255 Network 4
The last one is always 255 at the end and again all ones in any subnet is the broadcast address. So with subnetting you are making your network address bigger in an effort to segregate hosts for some reason. If the first bit is 0 in the IP address. It is a Class A address If the first two bits are 10 in the IP address. It is a Class B network If tthe first three bits are 110 in the IP address. It is a Class C network If the first four bits are 1110 in the IP address. It is a D Mulitccast address If the first four bits are 1111 in the IP addreess. It is Class E experimental |
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680 posts back to top |
| Posted 4 months ago my head hurts just thinking about it |
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| Posted 4 months ago I recommended this site quite a bit during my teaching days:
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