Question

. SSK Software Corp has offices in Toledo, Columbus and Pittsburg. Each office has 127 computers. The IT plan calls for connecting all offices using Routers. The Toledo site will also connect to the Internet. SSK Software Corp. has elected to use public IP address space on all computers at each of its sites. a) Their ISP has restricted the IP ranges to the ones below. The ISP’s Network Administrator is on vacation – you have been asked to fill-in and select a range of addresses that will satisfy SSK Software Corp.’s needs with the least amount of wasted IP addresses.

Propose a single range of addresses (using CIDR notation) for SSK Software Corp. and explain your answer. 201.137.136.0/24

201.138.135.0/24

225.113.8.0/24

225.113.9.0/24

192.168.0.0/16

201.138.136.0/24

201.138.137.0/24

206.122.148.0/24

10.0.0.0/8

201.138.138.0/24

201.135.138.0/24

201.136.137.0/25

201.138.139.0/24

b) Propose subnets for each of SSK Software Corp.’s offices using CIDR notation

Answer 1

a) Here given that we have to use CIDR means Classless Inter-Domain Routing, As per the question, the required number of IP addresses for each office is 127. We have given some IP addresses here which are named as public.

201.137.136.0/24

201.138.135.0/24

225.113.8.0/24

225.113.9.0/24

192.168.0.0/16

201.138.136.0/24

201.138.137.0/24

206.122.148.0/24

10.0.0.0/8

201.138.138.0/24

201.135.138.0/24

201.136.137.0/25

201.138.139.0/24

Let us examine which of these IPs are apt for those 3 offices.

As we know that as it is a CIDR notation the total available IPs for use will be 2^32-n for a given IP with CIDR.

Lets consider 192.168.0.0/16 and 10.0.0.8/8 comes under private IP range. But as they are given as publically available IPs we will check the IPs that can be given in that network. IN 192.168.0.0/16 we can assign 2^16 -2 Ip address and for 10.0.0.0/8 we will have 2^24 -2 IPs. So this leads to wastage of many IPs as we need only 127 IPs for an Office.

Now if we consider 201.136.137.0/25 we can assign 2^7 -2 IPs means 126 IPs because one IP will assign to network and another IP will be assigned to broadcast. But here we need 127 so we can't use this IP. The better IPs are with /24 notation as it can hold 256 IP addresses for each and we need 127 IP for each.

So these IPs can be used:-

201.137.136.0/24

201.138.135.0/24

225.113.8.0/24

225.113.9.0/24

201.138.136.0/24

201.138.137.0/24

206.122.148.0/24

201.138.138.0/24

201.135.138.0/24

201.138.139.0/24

We can choose any three IP address range from the above IPs as each range will be given with 254 hosts.

b) When coming to subnets for given offices here every office needs 127 host IP addresses. So, here are the IPs assigned to those offices with CIDR notation.

Toledo Office:- 201.138.139.0/24

Columbus Office:- 201.135.138.0/24

Pittsburg office:- 201.138.137.0/24

As each office going to be assigned with 254 hosts and each office need 127. This is the best CIDR notation for the network.

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