1. Configuring Subnetting
Module 6
H3065S F.00

2. Limitations of Large Networks
[Course Title]
[Module Title]
Limitations of Large Networks
/8 networks provide ~16 million host addresses
/16 networks provide ~65 thousand host addresses
Reasons for not putting 65 thousand hosts on one network:
packet
65,000 hosts
Topological Limitations
Excessive Collisions
Administrative Challenges
Poor Network Performance
. . .
H3065S F.00
© 2005 Hewlett-Packard Development Company, L.P.
[Rev. # or date]

3. [Course Title]
[Module Title]
Subnetting Concept
Break a large network into more manageable subnetworks
Example: Subnetting a /16 network
Subnet
(254 hosts)
Router
Network /16
(65,535 hosts)
Subnet
(254 hosts)
Router
Subnet
(254 hosts)
Router
Non-subnetted network:
one network with 65,535 nodes
Subnetted network:
254 subnets, each with 254 nodes
H3065S F.00
© 2005 Hewlett-Packard Development Company, L.P.
[Rev. # or date]

4. IP Addresses in a Subnetted Network
[Course Title]
[Module Title]
IP Addresses in a Subnetted Network
Non-subnetted network: IP addresses have two components.
Network Bits
Network Bits
Host Bits
Host Bits
Subnetted network: IP addresses have three components.
Network Bits
Network Bits
Subnet Bits
Host Bits
H3065S F.00
© 2005 Hewlett-Packard Development Company, L.P.
[Rev. # or date]

5. Netmasks in a Subnetted Network
[Course Title]
[Module Title]
Netmasks in a Subnetted Network
The netmask masks network and subnet bits with 1s.
Netmask for a non-subnetted /16 network: =
Network Bits
Network Bits
Host Bits
Host Bits
Netmask for /24 subnetworks on a /16 network: =
Network Bits
Network Bits
Subnet Bits
Host Bits
H3065S F.00
© 2005 Hewlett-Packard Development Company, L.P.
[Rev. # or date]

6. © 2005 Hewlett-Packard Development Company, L.P.
[Course Title]
[Module Title]
Subnet Addresses
Example: Network /16 subnetted into 254 subnets
st subnet
nd subnet
rd subnet
th subnet
th subnet
Network Bits
Network Bits
Subnet Bits
Host Bits
Netmask =
H3065S F.00
© 2005 Hewlett-Packard Development Company, L.P.
[Rev. # or date]

7. Host IP Addresses on a Subnet
[Course Title]
[Module Title]
Host IP Addresses on a Subnet
The host address with all 0s represents the address for the entire subnet.
The host address with all 1s represents the broadcast address for the subnet.
All other addresses within the subnet may be used for hosts.
Examples: IP addresses for subnet /24:
Subnet #1 : = /24
Host #1 : = /24
Host #2 : = /24
Host #3 : = /24
Host #253 : = /24
Host #254 : = /24
Broadcast : = . . .
Netmask =
H3065S F.00
© 2005 Hewlett-Packard Development Company, L.P.
[Rev. # or date]

8. Limitations of Subnetting on an Octet Boundary
[Course Title]
[Module Title]
Limitations of Subnetting on an Octet Boundary
How would you subnet your network, if . . .
You have a /24 network address?
You want exactly six subnets from a /16 network address?
H3065S F.00
© 2005 Hewlett-Packard Development Company, L.P.
[Rev. # or date]

9. Subnetting on a Non-Octet Boundary
[Course Title]
[Module Title]
Subnetting on a Non-Octet Boundary
Example: Network /24 subnetted into 6 subnets:
st subnet
nd subnet
rd subnet
th subnet
th subnet
th subnet
Network Bits
Network Bits
Network Bits
Subnet
Bits
Host
Bits
Netmask =
H3065S F.00
© 2005 Hewlett-Packard Development Company, L.P.
[Rev. # or date]

10. Routers in a Subnetted Network
[Course Title]
[Module Title]
Routers in a Subnetted Network
Facilities subnet ( /27)
Router
Manufacturing subnet ( /27)
Marketing subnet ( /27)
Finance subnet ( /27)
H3065S F.00
© 2005 Hewlett-Packard Development Company, L.P.
[Rev. # or date]

11. Configuring Subnetting
[Course Title]
[Module Title]
Configuring Subnetting
Facilities subnet ( /27)
/27
/27
Manufacturing subnet ( /27)
/27
HostA
/27
HostB
/27
HostC
HostA# ifconfig lan netmask up
HostA# route add default
H3065S F.00
© 2005 Hewlett-Packard Development Company, L.P.
[Rev. # or date]

12. © 2005 Hewlett-Packard Development Company, L.P.
Lab
activity
[Course Title]
[Module Title]
H3065S F.00
© 2005 Hewlett-Packard Development Company, L.P.
[Rev. # or date]

13. © 2005 Hewlett-Packard Development Company, L.P.
[Course Title]
[Module Title]
H3065S F.00
© 2005 Hewlett-Packard Development Company, L.P.
[Rev. # or date]