supernetting question

hi, I need some help with a problem involving supernetting. If I have 2 companies and one of them has 10 departments and a class C address 195.78.63.0 and the other one has 10 contigous class C addresses starting from 195.78.64.0, how do I create a supernetting chemem for these 2 companies? I am confused because I am nost sure if the 3rd octed of the starting address has to be divisible by 2 or by 19 in this case. And what role do the 10 departments of the 1st company play for the supernetting scheme? Thank you.

Hi gwydion,
you havnt mention how many systems will be in each department. ok as for 10 department you can use the following supernatting.


255.255.255.240

it gives 256-240=16-2=14 subnets each subnets having 14 host IP address....

so the 1st subnet IPs are 195.78.63.0 -195.78.63.15
2nd subnet IPs : 195.78.63.16 - 195.678.63.31
3rd Subnet IPs : 195.78.63.32 - 195.78.63.47 etc...

like this you may create the suprenat for other IPs too..


Hope it will help you

Hi gwydion,

company A
the one with 10 departments wil have a summary address of
195.78.63.0/24

Company B
you say they have 10 contiguous class c address 195.78.64.0 to 195.78.74.0

this can be summarized as 195.78.64.0/20 this will be seen by company A's router as one big supernet of 195.78.64.0/20

the mask of /20 will summarize upto a block of 16, so 195.78.64.0 to 195.78.79.0


well thats how I understand it.

oops, just realized these are not private address so maybe a block size of 8 would be a better answer.

Hi gwydion,

company A
the one with 10 departments wil have a summary address of
195.78.63.0/24

Company B
you say they have 10 contiguous class c address 195.78.64.0 to 195.78.74.0

this can be summarized as 195.78.64.0/20 this will be seen by company A's router as one big supernet of 195.78.64.0/20

the mask of /20 will summarize upto a block of 16, so 195.78.64.0 to 195.78.79.0


well thats how I understand it.

Thanks for that answer, i was struggling to see how you could fit just upto 195.8.74.0 range and thought you would have to go beyond it. Glad i was on the same wave length.

Hi Zenzippy,
How you applied block size 8 for your requirement. you said you need 10 IPs for each dept know then how come.

The possiblity is either you can use the block size 16 and above only.

can you tell me how you subnetted.