Suggestion for tips during the exam test?

pezhmankh · ‎04-05-2013

In the exams there are usually questions similar like "Which IP addresses are valid for hosts belonging to the 10.1.1.160/28 subnet" for this kind of problem I usually calculate the network and the broadcast address by adding the number 16 in this case to find out our network and broadcast number. Considering that there is no calculator in the exams and it could take a long time to calculate this kind of subnet problems, Does anyone has any tips to faster solve this kind of questions?

jimmysands73_2 · ‎04-05-2013

Practice, practice, practice.

I did so much practice once I called my girlfriend once 'Hey slash 22" lol

www.subnettingquestions.com is great also.

Rolf Fischer · ‎04-06-2013

Hi,

I think you already use the fastes way to solve such questions.

The subnet-bits tell you which byte to view, /25 - /32 => 4th byte (no great math here).

From /28 to /32 are 4 bits, 2^4=16

160:16=10, so the given network ID is valid.

Next /28 subnet is 10.1.1.176/28.

Broadcast is 10.1.1.175, host range is 10.1.1.161 - .174.

Normally you're allowed to make some notes during the exams.

So if you expect a lot of such questions in the exam, you can produce a table like this within a minute:

/15 /23 /31 > (2^1 =) 2 (256-2 =) .254

/14 /22 /30 > (2^2 =) 4 (256-4 =) .252

/13 /21 /29 > (2^3 =) 8 (256-8 =) .248

(...)

/8 /16 /24 > (2^8 =) 256 (256-256 =) .0

(of course, you need some practice)

With this, the rest is just counting.

Best regards,

Rolf