255.255.0.0 /16

neuregel

I can subnet C class forwards backwards in my head all day long, with B class starting with the /17 I can do the same. but when it comes to this /16 I have no understanding about what is trying to be accomplished.

Lammle does not explain /16 in either his ccent or ccna 6th editions ( if he does Im missing it)he does not cover class b subnetting on his video's and youtube offers no help that I found.

SdotLow

255.255.0.0 is what /24 is for class C addressing, but for class B. Everything in that second octet, 0-255 is considered a network. No hosts.

Same thing with Class A addresses and /8, or 255.0.0.0. Any time you see 255 in an octet, that is devoted to network addressing and nothing will be for host addressing. There are no network blocks or broadcast addresses in that octet. Only network.

So a class B with /16 -

172.16.0.0 /16 or 255.255.0.0. Your host range would be anything between 172.16.0.1 and 172.16.255.254. This is a pretty wasteful network, and probably one you won't see much if ever, but that's how it works.

VAHokie56

I always like to count backwards or forwards from /20 (255.255.240.0) so think of a /28 (255.255.255.240) as a /20 but in the second octet and do you math from there....err hope that helps

neuregel

okey so this clears things up a bit THnaks.

Ltat42a

neuregel wrote: »

I can subnet C class forwards backwards in my head all day long, with B class starting with the /17 I can do the same. but when it comes to this /16 I have no understanding about what is trying to be accomplished.

Lammle does not explain /16 in either his ccent or ccna 6th editions ( if he does Im missing it)he does not cover class b subnetting on his video's and youtube offers no help that I found.

Mr Lammle explains subnetting Class B addresses in his 6th edition. He shows you the steps then has several examples. At the end of the Class B section, he shows how to do it in your head.

Look in Chapter 3 - Subnetting


hth