CCNA ITN: Module 11

IPv4 address structure

32-bit address with network and host portions

Subnet mask

defines which bits are network vs. host

Prefix length

number of 1s in subnet mask, shown as /n

Network address

all host bits are 0

Broadcast address

all host bits are 1

Host address

any unique combination of 0s and 1s in host portion

Unicast address

one-to-one communication, 1.0.0.1–223.255.255.255

Broadcast address

one-to-all communication, 255.255.255.255

Multicast address

one-to-group communication, 224.0.0.0–239.255.255.255

Private address

internally used IPs: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16

Public address

globally routable, assigned by IANA/RIR

NAT

translates private IPs to public for Internet access

Loopback address

127.0.0.0/8, used to test TCP/IP stack

Class A IP

0.0.0.0/8 to 127.0.0.0/8, large networks

Class B IP

128.0.0.0/16 to 191.255.0.0/16, medium networks

Class C IP

192.0.0.0/24 to 223.255.255.0/24, small networks

Class D address

multicast range 224.0.0.0 to 239.255.255.255

Class E address

reserved for experimental use, 240.0.0.0–255.255.255.255

Subnetting

breaks a network into smaller, more manageable parts

Broadcast domain

area of network receiving broadcast frames

Subnet by

octets: /8, /16, /24—based on need

/24 subnet

254 usable hosts, easy to subnet

Magic number

256 - subnet mask octet, used to find subnet range

/16 subnet

subnetting starts in 3rd octet, good for medium-large networks

/8 subnet

subnetting starts in 2nd octet, good for very large networks

VLSM

variable-sized subnets, avoids wasted IP space

Subnetting requirements

consider host count, subnet count, future growth

Address plan

defines static/dynamic, private/public usage, and DHCP setup

VLSM best practice

start from large subnets, break into smaller ones

Address planning

critical for IPv4, especially with NAT and DHCP

DMZ

subnet that connects public-facing servers to the internet