Subnetting Operations

Why Subnet?

• Security

• Scalability

• Performance

• Segmenting the network into different pieces.

  • Control how many broadcast there are and how they get sent across the network

From One to Many

• 10.0.0.0 /8
  • 1 Network
  • 16,777,216 host
  • 10.0.0.1 - 10.255.255.255

Octal boundaries

• 10.0.0.0 /16
  • 255.255.0.0
  • 256 networks
  • 65,534 hosts per network
    • Very broad
• 10.0.0.0 /24
  • 255.255.255.0
  • 65,536 networks
  • 254 hosts per network
    • The longer the mask, the less the hosts
    • a /32 is enough for 1 IP address

From One to Many

• 10.x.y.z
  • X Site
  • Y VLAN
  • Z Host
• Logical
• One size may not fit all!

Variable-Length Subnet Masking (VLSM)

• 10.Site.Vlan.Hosts
• Need more than 254 hosts!
• Borrow bits from next octet
• 10.1.0.0/23

Bit Weight