Is this a valid question (related to subnetting)

dissolved

This is from my Sybex book. The objective was to find the mask.

1. 192.168.100.17, with 4 bits of subnetting
Since it was a class C, I said 255.255.255.240 as the mask.
Now I know that is right. But what if the numbers were:

172.16.0.1 with 4 bits of subnetting

Would the mask change to 255.255.240.0 ?


10.0.0.1 with 4 bits of subnetting. What would the mask be then?

255.240.0.0?

Help, am I doing this wrong?

smooth7905

its 172.16.0.0 /12 so with 4 bits of subnetting it would be 172.16.0.0/16 or
255.255.0.0

amod_pandya

acc to me...you are right (the orig poster)

172.16.0.1 with 4 bits of subnetting ..mask would indeed be 255.255.240.0
Since 172.16.0.1 is a class B address it has 16 bits of network...and as 4 bits are going towards subnet it leaves 12 bits for the host so the mask should have 12 zeros or /20 as the mask or 255.255.240.0

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10.0.0.1 with 4 bits of subnetting will have 255.240.0.0 as the mask.

Since 10.0.0.1 is a class A address it has 8 bits of network...and as 4 bits are going towards subnet it leaves 20 bits for the host so the mask should have 20 zeros or /12 as the mask or 255.240.0.0

hope it helps.

2lazybutsmart

yeah, I agree with amod.

If you say 4 bits, then that's 4 bits. period.

The only difference with the various classes is that 4 subnet bits would mean the same number of subnets (with the same subnet ID's) but a greater number of hosts .

2lbs.

dissolved

thanks guys