Chapter 5b

 Upon completion of this chapter, you should be able to:  Subnet an IPv4 address to make separate networks out of one address given  Use the new subnet mask to identify the subnet  Assign IPv4 addresses to hosts within your network  Identify each subnet’s new network ID and broadcast address  Find the network, broadcast, or check if the address is a valid host address by working backwards

5.1.3

Network Subnetwork Hosts

 Borrow bits from host portion to make new networks  Ask yourself…  How many networks do you need?  How many hosts per network are there?

 You MUST borrow at least 2 bits or leave at least 2 bits  Class C has 1 octet to borrow from  Class B has 2 octets to borrow from  Class A has 3 octets to borrow from  Remember the powers of 2  2 2 = 4  2 3 = 8  2 4 = 16  2 5 = 32  2 6 = 64 Remember 2 addresses you can’t use: Network & Broadcast

( ) ( ) ( ) ( ) ( ) ( )  Total Range #3  Useable Range #2  Network ID  /27  Broadcast Address  /27

 A packet with a destination IP of goes to a router  It ANDs to come up with the NETWORK #

 /28  What class address? C: Only deal with the last octet!    How many bits borrowed? = 16 networks  How many bits left over? = 16 hosts per sub-network

 Based on the IP address & SM, identify…  The network address  The broadcast address  How many bits were borrowed  How many bits were left over  Is the address valid

 PC1 has an address of /28. PC2 has an address of /28. Both are connected to a switch but they cannot communicate. The switch is working normally as are the PC’s NICs and Ethernet cables. Are the hosts on the same network or separate?

 What’s the broadcast address for /24?   Default SM, no subnetting  Sam’s Beef Hut uses network & to create subnets. How many useable hosts can be created per network?  14

 Which class gives you the most hosts/network? AA  Which class give you the most networks? CC  Public IP addresses must be __________.

5.1.5

 Allows you to use part of the address for the network portion  Called partial subnetting or VLSM  CIDR allows this  Helps reduce wasted addresses  You can subnet for each unequal network  Your address is /26 Net A needs 37 hosts Net B needs 15 hosts Net C needs 100 hosts

 Instead of having multiple subnet entries for each router port, CIDR uses the common bits to make ONE routing table address per port.

Chapter 5b