CCNA, CCNA Exam, CCNA help, Cisco Certified Network Associate, CCNA study, CCNA prep

CCNA 3.2.a: Prefix

Overview:

A prefix is simply the network address. In a routing table, the prefix is the destination network address.  A prefix-length is just the shorthand way to express a subnet mask using CIDR notation.  If the subnet mask is 255.255.255.0 than the prefix-length is /24.

Study Notes:

• Reading the routing table from top to bottom you can see the prefixes and prefix-lengths for the destination networks:
  • 0.0.0.0/0    The prefix is 0.0.0.0 and the prefix-length is /0
  • 172.16.0.0/16    The prefix is 172.16.0.0 and the prefix-length is /16, but this isn't a route just a summary
  • 172.16.1.0/24    The prefix is 172.16.1.0 and the prefix-length is /24
  • 172.16.1.1/32    You got this
  • 172.16.2.0/24    I'll show a couple more to make sure
  • 172.16.3.0/24
  • 172.16.4.0/28
  • 192.168.0.0/16    The prefix is 192.168.0.0 and the prefix-length is /16
  • 209.165.200.0/24
  • 209.165.200.224/30
  • 209.165.200.224/32
  • 209.165.200.225/32    The prefix is 209.165.200.225 and the prefix-length is /32
  • 209.165.200.228/30
  • 209.165.200.232/30
  • 209.165.200.233/32