Subnetting help::

Could someone please explain a fast method of working this out please:

What is the broadcast address of the network 172.29.144.0/23?

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Comments

lantech

Have you read this thread?

http://www.techexams.net/forums/ccna-ccent/38772-subnetting-made-easy.html

anobomski

lantech wrote: »

Have you read this thread?

http://www.techexams.net/forums/ccna-ccent/38772-subnetting-made-easy.html

that one does it for me every time.

NetworkVeteran

Ola_CISCO wrote: »

Could someone please explain a fast method of working this out please:

What is the broadcast address of the network 172.29.144.0/23?

/8 would be 172.x.x.x, /16 would be 172.29.x.x, /24 would be 172.29.144.x with a broadcast of 172.29.144.255. This is a /23, so the third octet's last bit (the one's place) is involved--we must switch that bit to a 1. So, 172.29.145.255.

Ola_CISCO

Thanks Guys, Now its clicked Phew!

mella060

Ola_CISCO wrote: »

Thanks Guys, Now its clicked Phew!

That was quick lol. Your first post implied that you was new to subnetting (correct me if i am wrong) and now you can do it in your head in 30 seconds or less. Nice work !!

Anyway a quick way to find the answer is to find the increment. A /23 prefix means that you have an increment of 2 in the 3rd octet. So you just go up by two in the third octet.

Subnets would be...

172.29.0.0 /23
172.29.2.0 /23
172.29.4.0 /23 etc

Since the subnets are incrementing or going up by two, just start at x.x.140.0 or x.x.142.0

For example...

172.29.140.0/23
172.29.142.0/23
172.29.144.0/23 - Usable addresses 172.29.144.1 - .145.254..Broadcast address is .145.255
172.29.146.0/23

This is all done in my head in the space of 15 - 30 seconds. After you subnet for a while you should be able to just look at a question and pretty much straight away find the general answer.

Ola_CISCO

@ mell060 I'm still working on doing it in my head in 30 secs lol, at the moment I'm still using my trusty pen and pad, from my first post I just needed a method of working it out quickly. Thanks for the breakdown !

fadhil

Ola_CISCO wrote: »

Could someone please explain a fast method of working this out please:

What is the broadcast address of the network 172.29.144.0/23?

to do that question first find the block size.
from this ip address 172.29.144.0/23, remember that /23 give subnet mask of 255.255.254.0
hence to get block size 256-254= 2. block size of 2.
networks:
172.29.144.0
172.29.146.0
172.29.148.0
172.29.250.0 and etc.
from network 172.29.144.0
host will be assign from 172.29.144.1 to 172.29.145.254 and broadcast address is 172.29.145.255.