1. What subnet mask should UNI change to and use if they want to have up to 50 different subnetworks in the uni.edu domain? Note: UNI network address is 134.161.0.0 for the class B network. 5 6 ANSWER: Since 50 is between 32 and 64, i.e. 50 < 2 and 50 > 2 we know that 6 bits will be needed to specify the SUBNETwork at UNI. 5 bits would only allow up to a maximum of 32, which is not enough, but 6 will do it, allowing up to 64 subnets. So the subnet mask should be 255.255.252.0 for UNI. 11111111.11111111.11111100.00000000 n = network address nnnnnnnn nnnnnnnn sssssshh hhhhhhhh s = subnet address -------- -------- $$$$$$== ======== h = host address bits 1111111 1 12345678 90123456 12345612 34567890 - = 16 network bits -------- -------- $$$$$$== ======== $ = 6 subnet bits 11111111.11111111.11111100.00000000 = = 10 host bits 255 255 252 0 ---- 32 bits = 4 bytes 255.255.252.0 is the subnet mask. 2. How many computers could be on each subnet for UNI, given the above subnet mask that you developed? 10 10 bits give ONE K or 1K or 2 or 1,024 different computer or host addresses, for EACH one of the up to 64 different subnetworks. 3. Answer questions #1 and #2 for UNI wanting to have up to 300 different subnets here in the uni.edu domain. ANSWERS: 8 Since 300 > 256, 8 bits is NOT ENOUGH. 2 < 300... Clearly, EIGHT IS NOT ENOUGH... So shall we try 9? 9 Let's try NINE bits. Wonderful! 512 > 300, and 2 > 300, so NINE bits would give us the capability to specify up to 512 different subnetworks, which is MORE THAN ENOUGH! Subnet mask would be 255.255.255.128.0, which is 11111111.11111111.11111111.10000000 nnnnnnnn nnnnnnnn ssssssss shhhhhhh 255 255 255 128 7 How many computer? 2 or 128 computers can be h for hosts, on each one of the up to 512 subnetworks. You have 7 bits to use to specify a host. 0000000 = 0 0000001 = 1 There are a total 0000010 = 2 of 128 different 0000011 = 3 7 "letter" words ... using the binary 1111100 = 124 alphabet or 0 and 1. 1111101 = 125 1111110 = 126 1111111 = 127 4. Suppose that the subnet mask for the middleearth.com domain is: 255.255.240.0 Group all of the following IP numbers for the named computers into groups that are on the same subnet. 144.154.31.44 Merry.middleearth.com 144.154.16.2 Aragorn.middleearth.com 144.154.16.3 Gimli.middleearth.com 144.154.220.111 Frodo.middleearth.com 144.154.100.111 Bifur.middleearth.com 144.154.213.111 Bilbo.middleearth.com 144.154.125.111 Bofur.middleearth.com 144.154.223.111 Gollum.middleearth.com 144.154.111.111 Strider.middleearth.com 144.154.208.222 Gandalf.middleearth.com 144.154.16.4 Legolas.middleearth.com 144.154.17.4 Samwise.middleearth.com 144.154.19.4 Boromir.middleearth.com 144.154.244.244 Sauron.middleearth.com You can just mention the computer name when you do the grouping, and avoid writing the .middleearth.com every time. ********************* SOLUTION ********************************* * * * Note: See following at the URL: * * http://www.cns.uni.edu/~jacobson/023/hobbits.txt * * from a separate browser session, so you can look * * at question #4 and this answer at the same time, * * if you do not have your original handout handy. * **************************************************************** obase=2 31 = 0001 1111 Merry Subnetwork address is 144.154.16.0 or 0001 16 = 0001 0000 Aragorn -- or 1 (one) 16 = 0001 0000 Gimli 16 = 0001 0001 Legolas 17 = 0001 0001 Samwise 19 = 0001 0011 Boromir 100 = 0110 0100 Bifur Subnetwork address is 144.154.96.0 or 0110 111 = 0110 1111 Strider -- or 6 (six) 125 = 0111 1101 Bofur Subnetwork address is 144.154.112.0 or 0111 --- or 7 (seven) 220 = 1101 1100 Frodo Subnetwork address is 144.154.208.0 or 1101 213 = 1101 0101 Bilbo --- or 13 223 = 1101 1111 Gollum 11010000 = 128 + 64 + 0 + 16 208 = 1101 0000 Gandalf = 208 244 = 1111 0100 Sauron Subnetwork address is 144.154.240.0 or 1111 --- or 15 and Sauron.middleearth.com is the only unpaired computer all by itself in the listed collection, except for Bofur on subnetwork 144.154.112.0 shown above. Sauron and Bofur should get together! math-cs:~/web/023> bc bc 1.06 Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc. bc for b = basic c = calculator ibase=2 <---- change input base (ibase) to base two, by requesting ibase=2 11010000 <-- input is the binary number 11010000 208 <-- output is base ten number 208 <------- use control-d to exit bc calculator math-cs:~/web/023> math-cs:~/web/023>bc obase=16 <------------- base 16 (base sixteen) or hexadecimal will be the output base for bc 220 = DC 213 = D5 223 = DF See how base 16 could be useful! 208 = D0 D = 1101 and all of these begin with D or 1101 Call it (Frodo, Bilbo, Gollum, and Gandalf) the D network if you want, or the 208, which is 11010000 or 144.154.208.0 ---- 244 = F4 100 = 64 The 6 network or the 01100000 = 96 network for Bifur 111 = 6F ---- and Strider on 144.154.96.0 subnet. 31 = 1F The 1 network or the 16 (SIXTEEN) network, since 17 = 11 1 = 0001 and 00010000 = 16... 19 = 13 ---- 144.154.16.0 subnet... 16 = 10 For Merry, Aragorn, Gimli, Legolas, Samwise and Boromir.