Compute IP range given CIDR address

and I'm going to talk about how to do cider addressing and figure out what are the assignable IP addresses what's the range and what's the net mask so first we're going to start with this example and cider address of one 52.2 got one 36.0 /defaultstyle an IP address - 26 is six bits available for the host part so 2 to the 6 is 64 so there are 64 possible IP addresses in this range now remember that there are always two IP addresses that are reserved the first one is with the host part all zeros that's the network address okay the second one is with the host part all once that's the broadcast address so if somebody sends to that it goes to all of the hosts on that network so we subtract 2 from there and we end up with 62 assignable IP addresses all right okay now how do we figure out what the range of these addresses are so the easiest way to do this is to look at you know what are the bits in this address okay so if we have six bits in the host part the host part is always finding the rightmost part of the address so this last octet is eight bits long six of them are part of the host part so we really only need to write out the binary for this last octet so 0 is is 4 is a is 8 zeros now one thing to remember is if your network part is less than 24 then you're going to have some host parts in this host bits in this part of the address so don't think that just the last octet and the dotted decimal but that's where all the host part sleep that's not how ciderworks solder is based on the particular number of bits so if you had a cyber address where the network part is less than 24 you're going to have to go further in and converting the IP address to binary to figure out where you need to make the difference to figure out the range okay so this is the this is the last octet and and so what we know is the first assignable IP address is with all of the host bits 0 except for the last one ok so we have 6 host bits our host bits are these these last six these two guys and all the rest of them are part of the network address okay so if we make these all zeros except the last one these always stay the same then this is going to be 150 2.2.1 36.1 okay since 150 2.2.1 36 all those bits are part of the network part they never change they always stay the same so we're just looking at this last 10 so this is the first assignable IP address another easy way to do this is that you have the host host address which is all of the host bits 0 the first assignable IP address is all the host bits 0 except the last one so the first assignable IP address is always going to be 1 plus the network address so that's true sometimes the last assignable IP address can be a little bit tricky in this case it's not so we bring down the network part of the address and now we're going to put all of the bits to be all the host bits to be 1 except the last one remember all of those fits one is the broadcast offense right so the 152 $2 36 stays the same and and so now we end up with 62 that's that's what this is okay so the broadcast address in this case you may be used to thinking of the broadcast address is 255 Oleg that's the one but in this case for this network the Berlin current cast address is 150 2.2.1 30 6.63 just a host bits being one okay so how do we figure out what the net mask is now so the net mask is where we take all of the network bits we make the view one in all of the host bits and we make them be zero all right so eight ones is 255 so we know that these three octet Tsar all part of the network part so then we have 255 dot 255 dot 255 right so now we need to figure out what the last octet compete so for the net ask if network parts are once and the host parts are zeros okay and so then this is 192 okay we have 128 plus 64 right 255 255 255 192 is the net net ok this is the first assignable this is the last assignable and this is the net

Channel: Michele C. Weigle

Views: 55,903

Keywords: Classless Inter-Domain Routing, IP Address (Protocol), netmask

Id: ls1mMyfnaC0

Length: 6min 49sec (409 seconds)

Published: Fri Jun 06 2014