CCNA 3.1 Subnetting Basics

• Subnetting breaks one large network into several smaller networks
• IP subnet-zero is a command line that allows you to use the first and last subnet in network design
• Subnetworks are created by taking bits from the host portion of IP address and reserving them for subnet address
• Subnet mask is a 32 bit value that allows the recipient of IP packets to distinguish the network ID portion of the IP address from the host ID portion of the IP address
• Default subnet mask (starting):

• Classless Inter-Domain Routing (CIDR) is the method that ISPs use to allocate a number of addresses to a company/home/user
• Class A network address has CIDR value of /8 - /15
• Class A, B network address has CIDR value of /16 - /23
• Class A, B, C network address has CIDR value of /24 - /30
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