Tagged with subnet …

ip subnet-zero

What is IP Subnet Zero? Before we talk about the command, let’s ask ourselves, “In the first place, what is a zero subnet?” Under old IP subnetting rules, the all 0’s subnet was reserved for the network, and the all 1’s subnet was reserved for the broadcast. Over time, engineers found that the all 0’s … Continue reading →

Subnet Address Mapping

Subnet Address Mapping This service subcommand designates a public “apparent” IP Address to be shared by all computers in a private subnet. This permits an ISP (for example) to assign a single public IP Address for use by all computers at a customer site. Command Syntax service [int] subnet [subnet address/bits] [app IP] service [int] … Continue reading →

How To Calculate a TCP-IP Subnet Mask

There are two main things to remember when trying to calculate subnets. The first is that that default subnet for a range is 255.255.255.0. This subnet, that we all recognize gives you one network with 255 different addresses from 1 to 255. Fairly easy stuff so far. The second thing to remember is the formula … Continue reading →

Subnet Mask Reference Table

Subnet size (# of hosts) Subnet Mask First host in block 2 hosts 255.255.255.252 1,5,9,13,17,21,25,…. 3 – 6 255.255.255.248 1,9,17,25,33,… 7 – 15 255.255.255.240 1,17,33,49,65,… 16 – 31 255.255.255.224 1,33,65,97,129,… 32 – 63 255.255.255.192 1,65,129,193,… 64 – 127 255.255.255.128 1 & 129 128 – 255 255.255.255.0 1 256 – 511 255.255.254.0 1,5,9,13,17,21,25,…. 512 – 1023 … Continue reading →

Subnetting Notes

Boolean Logic 0 AND 0 = 0 0 AND 1 = 0 1 AND 0 = 0 1 AND 1 = 1 0 OR 0 = 0 0 OR 1 = 1 1 OR 0 = 1 1 OR 1 = 1 Useful Graph This graph helps me reduce the number of errors I make … Continue reading →

Understanding the /24 after the IP

Sometimes people can find an IP written like 192.168.0.1/24 and they wonder about what that means, here’s a good explanation: IP addresses are written in decimal notation but are best understood in binary. Decimal is what we count in and goes from 0 to 9 – hex foes from 0 to 1 (0,1) giving 2 … Continue reading →