a. Consider an IP subnet with prefix 129.17.129.97/27. Provide the range of IP a

Question

a. Consider an IP subnet with prefix 129.17.129.97/27. Provide the range of IP addresses (of form
xxx.xxx.xxx.xxx to yyy.yyy.yyy.yyy) that can be assigned to this subnet. (2 pt) (show all the
details/work)
b. Suppose an organization owns the block of addresses of the form 129.17.129.97/27. Suppose it
wants to create four IP subnets from this block, with each block having the same number of IP
addresses. What are the prefixes (of form xxx.xxx.xxx/y) for the four IP subnets? (8 pt) (show all the
details/work – include assumptions made)

Explanation / Answer

CIDR Notation:

CIDR means classless inter domain routing
in the below we are using CIDR notation to assign ip addresses to the networks.
it helps to assign ip address to networks continuouly unlike Class based addressing in which we need to use only specified range of addresses.
in CIDR we represent an ip address range as follows
xxx.xxx.xxx.xxx/xx
example: 192.168.0.15/24

it represents for the given network we are using 24 bits as network address and remaining are range of ip addresses

example:

192.168.0.15/24 = 11000000.10101000.00000000.00001111

in the above address we consider 24 bits as network address there fore it is

11111111.11111111.11111111.00000000 = it represents we have 8 remaining bits to range of ip address and we calculate that range as follows

2^8 - 1 = 256-1 = 255

so the for the above the ip address range is 255 so that we can use 255 address in a subnet.

Solutions for the given:

a)

for this we have 27 bits of network address and 5 bits for range of ip's

so the number of addresses that can be assigned for given CIDR notation is 2^5-1 = 31 and 1 additional address for broadccast address so total we have 32 address

and we use 1 previous address for interconnectvity and internet so we cnsider network addresses from 129.17.129.96 and from that 31 addresses becomes our address range

therfore our address range is 96 - 127

the range of ip's are 129.17.129.96 to 129.17.129.127

b)

for the given CIDR ip address we have 31 ip addresses as shown above in this we have to divide those 32 addresses into 4 subnets 32/4 = 8 i.e., in each subnet we have 8 IP addresses and for 8 address we represent 29 bits of ip address as network addresses so we have CIDR notation /29

subnet1: 129.17.129.96/29 to 129.17.129.103/29
subnet2: 129.17.129.104/29 to 129.17.129.111/29
subnet3: 129.17.129.112/29 to 129.17.129.119/29
subnet4: 129.17.129.120/29 to 129.17.129.127/29

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