1.7: IPv4 Addressing & Subnetting

IP

Network Address that contains two, four-octet values; the unique protocol address, and the subnet mask

Subnet Mask determines the subnet in which the device is located

Default Gateway

The router that allows you to communicate outside your local subnet

Must be an IP address on the local subnet

Loopback

Special IP address that addresses to yourself

Ranges from 127.0.0.1 through 127.255.255.254

Easy way to self-reference, good way to confirm that your IP stack is working properly

Reserved

Special IP addresses dedicated for future use

Ranges from 240.0.0.1 through 254.255.255.254

All of these addresses are Class E

Virtual IP

Special IP addresses not associated with physical network adapters

Used for VMs, internal routers, etc.

APIPA

Networking feature for providing link-local addresses for comms to other local devices, no forwarding by routers

Used when DHCP is not available, assigned with ARP; Functional block from 169.254.1.0 through 169.254.254.255

Automatic Private IP Addressing

Private

IP addresses that cannot be used publicly, and defined in RFC1918

Helps alleviate the issue of public IP exhaustion; use NAT to communicate with public internet

Huge ranges available; properly design and scale large networks

A

IPv4 Address Class where the leading address ranges from 1-127

Default Subnet Mask: 255.0.0.0

8 network bits, 24 host bits

B

IPv4 Address Class where the leading address ranges from 128-191

Default Subnet Mask: 255.255.0.0

16 network bits, 16 host bits

C

IPv4 Address Class where the leading address ranges from 192-223

Default Subnet Mask: 255.255.255.0

24 network bits, 8 host bits

D

IPv4 Address Class where the leading address ranges from 224-239

No Default Subnet Mask; network and remaining bits undefined

Used for Multicast addresses

E

IPv4 Address Class where the leading address ranges from 240-254

No Default Subnet Mask; network and remaining bits undefined

Used for Reserved addresses