# IP Addressing/Subnetting Simplified - create-california-online

Networking and Communications

Oct 24, 2013 (4 years and 7 months ago)

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Simplified

Brian Sterck

May 6, 2005

Class A

Subnetting

Options

Class B

Subnetting

Options

Class C

Subnetting

Options

Brain Benders

More Tools…

Practical Example

allocated?

How many are needed?

LANs =

14+10+19+23+6+17+14 = 103

WANs = 4+4+4+4+4+4 = 24

Total = 103 + 24 = 127

Understanding IP Requirements

Subnetworks on the LAN/WAN need to be
issued using perfect powers of 2

2
2 =
4

2
3 =
8

2
4 =
16

2
5 =
32

2
6 =
64

2
7 =
128

Scaling Subnets

With a requirement of 23 nodes…

The next perfect power of 2 that meets this
need = 32

2
5

= 32 5 host bits needed

Last Octet is then represented as:

A.B.C.
NNN
HHHHH

N=Network

H=Host

11111111.11111111.11111111.
111
00000

Subnetting Examples

# Hosts

255.255.255.0

/24

256 (254)

255.255.255.128

/25

128 (126)

255.255.255.192

/26

64 (62)

255.255.255.224

/27

32 (30)

255.255.255.240

/28

16 (14)

255.255.255.248

/29

8 (6)

255.255.255.252

/30

4 (2)

Practical Example

LANs =

16+16+32+32+8+32+16 = 152

= /28 + /28 + /27 + /27 + /29 + /27 + /28 = 152

WANs = 4+4+4+4+4+4 = 24

= /30 + /30 + /30 + /30 + /30 + /30 = 24

Total = 103 + 52 = 157

Reference Points

Use numbers, symbols, letters to represent

Use some consistent method for assignment

Size of Subnetwork

Location

Zone or Distribution Point

Assign Reference Points

Subnetting Options

Subnetting Options (cont.)

VLSM and Routing Protocols

Does your routing protocol support varying
the length of the subnet mask from one
interface to another?

Can you re
-
subnet a subnet differently
from one interface to another and still
RIPv2, OSPF, EIGRP, ISIS, BGP?

Routing Protocols

Supporting VLSM

RIP version 2

EIGRP

OSPF

ISIS

Not Supporting VLSM

IGRP

RIP version 1

Which Routing Protocols will

Non
-
VLSM capable Routing

Protocols will work just fine!

Problem!

The 192.168.20.0 /24 network gives us:

1 Network

254 Nodes Available for Assignment

13 Subnetworks Required

Network Demands range from 4

32
nodes per LAN / WAN segment

Start Subnetting

Subnetting

Subnetting

Box Diagram Alternate

Future Expansion Danger

Note the three locations with the and

If we need to add a network printer or visitor
with laptop, the IP addressing scheme will have
to be modified.

This results in downtime and careful migration
planning

There must be a better way!