"Peter Koch" <pmk@deins.informatik.uni-dortmund.de> writes: * * Marten.Terpstra@ripe.net writes: * * > Havard.Eidnes@runit.sintef.no writes: * * [...] * If you have the need for two large subnets, you have to use a mask of 2:6 * (see below). This is bad, we have in some cases seen subnets of size 50-70 * and * then had to assign one C address for each of them. * * If you actually use subnetting 3:5, you have 2^3-2=6 subnets with * 2^5-2=30 hosts each. You have a maximum of 180 hosts here (router(s) not ta * ken * into account), an unsubnetted network would offer 254, so this is about 71 * %. * * Looking at all possible subnet masks, you get: * * subnet mask | # subnets | # hosts/subnet | total # hosts | usage * -------------+------------+----------------+---------------+------ * 1:7 | not allowed| | | * 2:6 | 2 | 62 | 124 | 49 % * 3:5 | 6 | 30 | 180 | 71 % * 4:4 | 14 | 14 | 196 | 77 % * 5:3 | 30 | 6 | 180 | 71 % * 6:2 | 62 | 2 | 124 | 49 % * 7:1 | not allowed| | | * * Percentage is nothing to worry about too much. * More address space would be wasted if you would assign a full class C net * for every subnet the requestor operates. Sorry about my fantastic calculations. You are of course right. I'll make sure I get some more coffee next time ;-) * Peter -Marten