> As for VLSM, I found an example in Jeff Doyle (TCP/IP Vol 1) on > p290 that I don't understand. > 192.168.50.0 /25, and it states that the reason it has /25 is > because it needs to have 100 hosts => so 2^7-2=126 hosts (as 2^6 would be too small), so it makes sense. > > What confuses me is that since 192.168.50.0 /25 is a Class C, > it uses up /24 for subnet bits: > > And if /25 - /24 = /1 > > But isn't the way the calculate the number of subnet: 2^n-2, > and in this case, 2^1-2 = 0, so does it mean it has no subnet? > Also, as for host address, how can I derive Jeff's answer as > the host range is 192.168.50.1-192.168.50.126?
Think of it this way.... 2^y-2 = subnets 2^x-2 = hosts x+y=8 So in a: /24 = 256 addresses (.0-.255) /25 = 128 addresses (.0-.127) .0 is always for the network address and .127 or the last IP in a subnet is for the broadcast, .1 or any other IP(except network/broadcast) can be used as the gateway and the rest for the host IP's. HTH's John CCNA Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35905&t=35827 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
