Question : Cisco Networking: How to determine if CIDR address is Network or Broadcast

Hello experts,

I need some help with classless ip addresses. I need a proven consistent method of determining if a cidr address is a network address or a broadcast address.

My method is solid and consistent. However, it takes rather long and it is not timed-test friendly if you know what I mean.

Lets say I have a few addresses in a multiple choice that i need to assign to interfaces. These addresses can have huge numbers. How can I determine quickly if that address is a network or broadcast. I will award maximum points for good explanations and for follow-up questions I may have.

Thanks.

Answer : Cisco Networking: How to determine if CIDR address is Network or Broadcast

I don't have a majic mathmatical formula for you, but it's not too terribly difficult to recognize broadcast addresses.
With any notation less than or equal to /24 (/8.../16 /17/18/../24), any broadcast address MUST end with .255, ie.
174.75.9.255 /23
10.1.11.255 /22
With notation > /24 (/25..../30) there are only a few possibilities, always odd number, easy to remember table:
/25 = .127 or .255
/26 = (add 64)  .63 .127 .191 .255
/27 = (add 32) .31 .63 .95 .127 .159 .191 .223 .255