addressing in tcpip networks-v2

8/22/2019 Addressing in TCPIP Networks-V2

1/47

Internetworking With TCP/IP

IPv4 Addressing in

Ethernet, IEEE 802.3, Token Ring, X.25, SNA, FDDI, .

TCP UDP

Telnet Gopher NFS

FTP X Win TFTP

SMTP SNMP

REXEC DNS RPC

Application Layer

Transport Layer

Network Layer

Link Interface

ICMP IGMPIP RARPARP

Parviz Kermani


2/47

Legends

Back to previous foil

Page contains animation

End of animation

2IP Addressing


3/47

Acknowledgement

Part of the following pages were taken frommaterials provided by other authors andcompanies

CiscoLecture slides of Computer Networking: A TopDown Approach by J im Kurose and Keith Ross

CCENT/CCNA ICND1 & 2- Official Exam

Certification Guide, Wendell Odom, Cisco Press

3IP Addressing


4/47

Internet in a Nutshell

Ethernet, IEEE 802.3, Token Ring, X.25, SNA, FDDI, .

TCP UDP

Telnet Gopher NFS

FTP X Win TFTP

SMTP SNMP

REXEC DNS RPC

Application Layer

Transport Layer

Network Layer

Link Interface

ICMP IGMPIP RARPARP

4IP Addressing


5/47

Addresses & Names

Hardware (Layer 2)

Lowest level

Ethernet (MAC), Serial point-to-point, ..

Network (Layer 3)

IPIPX, SNA, others

Application (layer 5?)

Names (URL), alias, ..

All are important and needed

Ultimately, all deliveries move over the physical layerNote: Port address not under discussion (Transport)

5IP Addressing


6/47

Layer 2 Addressing

Uses MAC address

Assigned to end devices

6IP Addressing


7/47

Layer 3 Addressing

Each Network Architecture has its own Layer 3 address format.

OSI uses NSAP.

TCP/IP uses IP

7IP Addressing


8/47

Host-to-Host Packet Delivery (1 of 10)

8IP Addressing


9/47


9IP Addressing


10/47


10IP Addressing


11/47


11IP Addressing


12/47


12IP Addressing


13/47


13IP Addressing


14/47


14IP Addressing


15/47


15IP Addressing


16/47


16IP Addressing


17/47


17IP Addressing


18/47

(Classical) IP Addressing (Layer 3)

IP address is 32 bit

An An IP address is broken in two parts

Network address

Host address

The division between network and host isdetermined by the size of network anddetermined by the class of the address

Network host

18IP Addressing


19/47

IP Addresses

classful addressing

0 network host

10 network host

110 network host

1110 multicast address

A

B

C

D

class

1.0.0.0 to

127.255.255.255

128.0.0.0 to

191.255.255.255

192.0.0.0 to

223.255.255.255

224.0.0.0 to

239.255.255.255

32 bits

19IP Addressing


20/47

IP Addresses

IP Classful Addresses:Class A addresses begin with 0xxx, or 1 to 126

Class B addresses begin with 10xx, or 128 to 191

Class C addresses begin with 110x, or 192 to 223

Class D addresses begin with 1110, or 224 to 239Multicast

Class E addresses begin with 1111, or 240 to 254Experimental

20IP Addressing


21/47

Classful Addressing

Number ofelements in each class

Class Number ofclasses

Number of localaddresses

A 0xxx 128 16,777,216

B 10xx 16,384 65,534

C 110x 2,097,152 254

21IP Addressing


22/47

Private IP Addresses Space

Private IP Networks Class of

Network

Number of

Networks

10.0.0.0 to 10.0.0.0 A 1172.16.0.0 to 172.31.0.0 B 16

192.168.0.0 to 192.168.255.0 C 256

IP Addressing 22

Note: The third column is the Number ofNetworks (and not IP Addresses)


23/47

Problems with Classful Addressing

Inefficient use of address space, addressspace exhaustion

e.g., class B net allocated enough addresses for65K hosts, even if only 2K hosts in that network

Network manageability (discussed below)

No longer formally part of IP addressingarchitecture

Note:A classful address identifies the Network andHost field

No need for Network Mask!

23IP Addressing


24/47

Manageability: Flat Topology

Problems

All devices share the same bandwidth.

All devices share the same broadcast domain.It is difficult to apply a security policy.

24IP Addressing


25/47

Manageability: Subnetworks

The Smaller networksare easier to manage.

Overall traffic isreduced.

You can more easily

apply network securitypolicies.

1-25IP Addressing


26/47

IP addressing: CIDR

CIDR: Classless InterDomain Routing

Adopted by IETF in 1993Network (subnet) portion of address of arbitrarylengthaddress format: a.b.c.d/x, where x is # bits in network(subnet) portion of address

To support 2000 hosts, a block of 2048 addresses of theforma.b.c.d/21 assigned

11 bits needed to store 2048 (211=2048)

In practice the 11 bit rightmost addressing could be furtherdivided (subnetting, more on this later)

11001000 00010111 00010000 00000000

networkpart

hostpart

152.23.16.0/21

26IP Addressing


27/47

Network Mask

With CIDR, address no longer specifies the networkportion

Mask is used to extract network portion from an IPAddress

A string of 32 bits

Bits corresponding to network (and subnet) part set to 1

Bits corresponding to host part set to 0

Ex (classful address):Addr = 9.2.225.65/8

= 00001001.00000010.11100001.01000001

Mask = 11111111.00000000.00000000.00000000

= 255 . 0 . 0 . 0

27IP Addressing


28/47

Mask examples (classful addresses)

Ex-1:Addr = 9 . 2 . 225 . 65/8

= 00001001.00000010.11100001.01000001

Mask = 11111111.00000000.00000000.00000000

= 255 . 0 . 0 . 0

N-Adr= 10001001.00000000.00000000.00000000

9.0.0.0

Ex-2Addr = 156 . 204 . 135 . 160/19

= 10011100.11001100.10000111.10100000Mask = 11111111.11111111.11100000.00000000

= 255 . 255 . 224 . 0

N-Adr= 10011100.11001100.10000000.00000000

156 . 204 . 128 . 0

28IP Addressing


29/47

Two-Level and Three-Level Addresses

Inefficiency of two-level addresses

A third level of addressing, consisting ofsubnets, was developed

Subnet address:The original classful networkportion plus a subnet field

Also known as extended network field

Subnet and host field created from the original

classful host portion

Subnet Mask helps identify the host/networkpart of an address

29IP Addressing


30/47

What a Subnet Mask Does

Tells the router the number of bits to look at whenrouting

Defines the number of bits that are significant

Used as a measuring tool, not to hide anything

30IP Addressing


31/47

Possible Subnets and Hosts for a Class CNetwork

31IP Addressing


32/47

Possible Subnets and Hosts for a Class BNetwork

32IP Addressing


33/47

Possible Subnets and Hosts for a Class ANetwork

33IP Addressing


34/47

End System Subnet Mask Operation

34IP Addressing


35/47

Topology Example

A network topology using one IP network with six subnets

35IP Addressing


36/47

How Routers Use Subnet Masks

36IP Addressing


37/47

Working with subnets and masks:Analysis

Analysis of a given IP address/maskBinary/decimal mask

Subnet number (network prefix)

Next/previous subnetRange of addresses

Broadcast address

The first IP address

The last IP addressImportant: are networks specified by 2 addressesoverlapping?

IP Addressing 37


38/47

Working with subnets and masks: Design

Choosing a subnet mask to meet designrequirements

Finding the only possible mask

Finding multiple possible masksChoosing the mask that maximizes the number ofsubnets or hosts

IP Addressing 38


39/47

Subnet addresses

Reserved addresses:The smallest address (all 0s) signifies the subnetnumber

128.12.17.144/28: x.y.z.10010000

10.12.16.128/26: x.y.z.10000000

The last address (all 1s) signifies the broadcastaddress

128.12.15.159/28: x.y.z.10011111

10.12.16.191/26: x.y.z.10111111

IP Addressing 39


40/47

Subnetting: A useful reference chart

IP Addressing 40


41/47

Example: 199.214.17.132/28 (Class C)

IP@:x.y.z.10000100Borrowed bits: 4; Net bits: 28; Host bits: 4

Block size 16

Mask(last byte only): 11110000; 240

Subnet number: 199.214.17.128 (10000000)Next/previous subnets:

Next: 128 + 16= 144 (10010000)

Previous: 128 16 = 112 (01110000)

Range of addresses: x.y.z.129 to x.y.z.143

Broadcast address: 199.214.17.143First IP address: 199.214.17.129

Last IP address: 199.214.17.142

IP Addressing 41


42/47

Example: 148.214.17.132/22 (Class B)

IP@:x.y.00010001.10000100Borrowed bits: 6; Net bits: 22; Host bits: 10

Block size: 4 (in the 3rd byte)

Mask: 1. 1.11111100.00000000; 255.255.252.0

Subnet number: 148.214.16.0 (0001000.00000000)Next/previous subnets:

Next: 16+4=20 (192.214.20.0)

Previous: 16-4=12 (192.214.12.0)

Range of addresses: 192.214.16.1 to 192.214.19.255)

Broadcast address: 199.214.19.255First IP address: 199.214.16.1

Last IP address: 199.214.19.254

IP Addressing 42


43/47

Example: 9.214.17.132/12 (Class A)

IP@:Borrowed bits: __; Net bits: __; Host bits: __

Block size: __ (in the __ byte)

Mask:

Subnet number:Next/previous subnets:

Next:

Previous:

Range of addresses:

Broadcast address:First IP address:

Last IP address:

IP Addressing 43


44/47

The Dread of Overlapping Subnets

In designing networks, care should be takento prevent overlapping subnets

Step 1: calculate the subnet number and

subnet broadcast address of each subnet.Determines range of addresses within eachsubnet

Step 2: Compare the range of addresses in

each subnet and look for any overlap

IP Addressing 44


45/47


Is there any flaw in the following network?

IP Addressing 45


46/47

Problem Network

IP Addressing 46

172.16.4.2/23

172.16.5.2/24

172.16.2.1/23

1

2

3


47/47


172.16.2.1/23Mask: 255.255.254.0

Subnet number: 172.16.2.0

Broadcast @: 172.16.3.255

172.16.4.1/23Mask: 255.255.254.0


Broadcast @: 172.16.5.255

172.16.5.1/24Mask: 255.255.255.0


Broadcast @: 172.16.5.255

Overlap!

addressing in tcpip networks-v2

Documents