Understanding Variable Length Subnet Masks

under construction

I just got out of ICRC where I learned about variable length subnet masking. I'm writing this document to

1. solidify the concepts in my brain
2. so someone else might learn too.

There may be some inaccuracies, so if you see any please let me know.

What is a subnet mask?

Subnet masks are used by hosts to determine network gateways and broadcast addresses.

What is a variable length subnet mask?

Explanations

• Webopedia: Subnet Mask
• 3Com: Understanding IP Addressing
• Connected: Subnetting
• Connected: Classless Inter-Domain Routing CIDR
• SIE: Custom Subnetting

Calculators and Tables

• Network Calculators
• SIE: Subnet Tables
• Perl Module Net::Netmask