subnet mask quick question

Karimbruxelles

Hi Guys,

On Class C adress, borowing 3 bits for the subnet mask e.g 255.255.255.224
Can I assign host address starting from 1,2,3 etc... or shall I start to assign adress from 32?

e.g

200.1.1.2
255.255.255.224

OR

I can only start from

200.1.1.33
255.255.255.224


Please help as now I'm really confus


Thanks

EdTheLad

Karimbruxelles wrote:

Hi Guys,

On Class C adress, borowing 3 bits for the subnet mask e.g 255.255.255.224
Can I assign host address starting from 1,2,3 etc... or shall I start to assign adress from 32?

e.g

200.1.1.2
255.255.255.224

OR

I can only start from

200.1.1.33
255.255.255.224


Please help as now I'm really confus


Thanks

This all depends if IP Subnet-Zero is enabled on your cisco router or not.
In early releases on cisco IOS subnet-zero was switched off by default meaning the first and the last subnet were not used.
So your above answer 200.1.1.33 255.255.255.224 would be correct.
Now cisco enables subnet-zero by default which means the first and last subnet are counted so your above answer 200.1.1.1 255.255.255.224 would be correct.
In the exam do not include subnet-zero if you are not explicitly told it is enabled.Now with reference to other ip vendor equipment like Riverstone,Alcatel,Redback blah blah blah they dont have the concept of subnet-zero and recognise all subnets by default.
Hope this helps,but if you read the forum you will see this has been discussed before!!!

Karimbruxelles

Thanks a lot for your quick answer

Cheers

Karimbruxelles

Karimbruxelles

But My 1st Hosts adress should start at 33 or ?
e.g 200.1.1.33 255.255.255.224

subnet number 200.1.1.32

Because if I use 200.1.1.3 255.255.255.224 for e.g
My subnet number will be 200.1.1.0

Could you please clarify this?

Thanks a lot

EdTheLad

with subnet-zero
subnets= 0,32,64,96......224
I think you should be able to work out the hosts?
If not read a book

without subnet-zero
subnets=32,64,96......192
I think you should be able to work out the hosts?
If not read a book

Karimbruxelles

OK I understand now

I'm so glad, thx matte