Table of Contents

  1. Packet Structure
  2. IP Classes and Ranges
  3. Subnets
  4. Notes
  5. More Resources

Packet Structure

Version Header Length ToS/DSCP Total Length
Identification Flags Fragment Offset
TTL Protocol Header Checksum
Source Address
Dest Address
Options Padding
Data

Wireshark IP Section

IP Classes and Ranges

Class CIDR Subnet Mask IP Range Description
A 0.0.0.0/1 128.0.0.0 0.0.0.0 - 127.255.255.255 Classful class A address space
10.0.0.0/8 255.0.0.0 10.0.0.0 – 10.255.255.255 Private class A addressing
127.0.0.0/8 255.0.0.0 127.0.0.0 - 127.255.255.255 Used for loopback addresses (localhost)
B 128.0.0.0/1 128.0.0.0 128.0.0.0 - 191.255.255.255 Classful class B address space
169.254.0.0/16 255.255.0.0 169.254.0.0 - 169.254.255.255 local link address
172.16.0.0/12 255.240.0.0 172.16.0.0 – 172.31.255.255 Private class B addressing
C 192.0.0.0/1 128.0.0.0 192.0.0.0 - 223.255.255.255 Classful class C address space
192.0.2.0/24 255.255.255.0 192.0.2.0 - 192.0.2.255 Used for documentation
192.168.0.0/16 255.255.0.0 192.168.0.0 – 192.168.255.255 Private class C addressing
224.0.0.0/4 240.0.0.0 224.0.0.0 - Global multicast
255.255.255.25532 255.255.255.255 N/A Global Broadcast

Subnets

CIDR Subnet Mask Wildcard Total IPs (-2*)
/32 255.255.255.255 0.0.0.0 1
/31 255.255.255.254 0.0.0.1 2
/30 255.255.255.252 0.0.0.3 4
/29 255.255.255.248 0.0.0.7 8
/28 255.255.255.240 0.0.0.15 16
/27 255.255.255.224 0.0.0.31 32
/26 255.255.255.192 0.0.0.63 64
/25 255.255.255.128 0.0.0.127 128
/24 255.255.255.0 0.0.0.255 256
/23 255.255.254.0 0.0.1.255 512
/22 255.255.252.0 0.0.3.255 1024
/21 255.255.248.0 0.0.7.255 2048
/20 255.255.240.0 0.0.15.255 4096
/19 255.255.224.0 0.0.31.255 8192
/18 255.255.192.0 0.0.63.255 16384
/17 255.255.128.0 0.0.127.255 32768
/16 255.255.0.0 0.0.255.255 65536
/15 255.254.0.0 0.1.255.255 131072
/14 255.252.0.0 0.3.255.255 262144
/13 255.248.0.0 0.7.255.255 524288
/12 255.240.0.0 0.15.255.255 1048576
/11 255.224.0.0 0.31.255.255 2097152
/10 255.192.0.0 0.63.255.255 4194304
/9 255.128.0.0 0.127.255.255 8388608
/8 255.0.0.0 0.255.255.255 16777216
/7 254.0.0.0 33554432
/6 252.0.0.0 67108864
/5 248.0.0.0 134217728
/4 240.0.0.0 268435456
/3 224.0.0.0 536870912
/2 192.0.0.0 1073741824
/1 128.0.0.0 2147483648
  • -2 for the number of usable IPs

Notes

Note Definition
# of subnets 2n
# of hosts 2(32-n)
Block size 256 - subnet mask
Broadcast Addr last addr in subnet
Usable Hosts Between network addr and broadcast

More Resources: