CODEWITHSUNDEEP
cidr
codigube
codigube

Reputation: 1256

CIDR /28 calculation confusion

I am trying to learn how to calculate IP addresses from CIDR block.

For example, 10.88.135.144/28 or 10.88.135.10010000/28

From what I understand, that means first 28 bits are associated with network address while the rest 4 bits are host addresses. That would result in following IP range:

10.88.135.10010000 - 10.88.135.10011111

The first IP should be 10.88.135.144 and last IP address should be 10.88.135.159

But according to cidr.xyz. The first IP should be 10.88.135.145 and the last one should be 10.88.135.158.

I really can't figure out why. Can anyone explain the reason for me? Thanks!

Upvotes: 0

Views: 276

Answers (1)

Prav
Prav

Reputation: 2884

Generally, the first IP is the network identifier and cannot be assigned to any device.This is used by router or switch on the network.

The last one is the broadcasting IP and cannot be assigned to any device as this IP is used by router or switch on the network to broadcast information.

https://www.quora.com/In-IP-addresses-what-is-meant-by-network-ID-and-host-ID

https://supportforums.cisco.com/t5/wan-routing-and-switching/what-is-broadcast-address/td-p/2494445#messageBodySimpleDisplay_1

Upvotes: 2

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