Network & broadcast address

• Network address: all host bits = 0
• Broadcast address: all host bits = 1

Example /24:

• Network: 192.168.1.0
• Broadcast: 192.168.1.255

Loopback

• Range: 127.0.0.0/8
• Typical: 127.0.0.1
• Used for: testing, router ID (OSPF/BGP)

APIPA

• Range: 169.254.0.0/16
• Used when DHCP fails
• Local communication only – no routing

Exam tips ⚠️

• APIPA address on a host → the DHCP problem is the first thing to check. Network = host bits 0, broadcast = host bits 1 – memorize it.