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Community Member

Block addresses

Hello. I need help with these questions. If you can help that would be appreciated.


An ISP is granted a block of addresses starting with The ISP wants to distribute these blocks to 2600 customers as follows.

a.The first group has 200 medium-size businesses; each needs 128 addresses.

b.The second group has 400 small businesses, each needs 16 addresses.

c.The third group has 2000 households; each needs 4 addresses.

Design the subblocks and give the slash notation for each subblock. Find out how many addresses are still available after these allocations.


Show in hexadecimal colon notation the IPv6 address

a. Compatible to the IPv4 address

b. Mapped to the IPv4 address

Cisco Employee

Re: Block addresses

Hi Eric,

Answer to question 1)

a) You may not get exact 200 subnets so the closest will be 256 subnets having 254 valid hosts per subnet so the mask will be or /24

b)Again you may not get exact 400 subnets so you have to compromise with 512 subnets with 126 valid hosts per subnet and the mask will be or /25

c)In last section also you may not get exact 2000 subnets so have to compromise with 2048 subnets and 30 valid host per subnet so the mask will be or /27

I am not an IPv6 guy so may not be able to answer your second question.



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