Internet Protocol

Network - IP Addressing and Subnetting

IP Address

• Layer 3 property
• Can be set automatically or statically
• Network and Host portion
• 4 bytes in IPv4 - 32 bits

Network vs Host

• a.b.c.d/x (a.b.c.d are integers) x is the network bits and remains are host
• Example 192.168.254.0/24
• The first 24 bits (3 bytes) are network the rest 8 are for host
• This means we can have 2^24 (16,777,216) networks and each network has 2^8 (255) hosts
• Also called a subnet

Subnet Mask

• 192.168.254.0/24 is also called a subnet
• The subnet has a mask 255.255.255.0
• Subnet mask is used to determine whether an IP is in the same subnet

Default Gateway

• Most networks consist of hosts and a Default Gateway
• Host A can talk to B directly if both are in the same subnet
• Otherwise A sends it to someone who might know, the gateway
• The Gateway has an IP Address and each host should know its gateway