1

IPv4 (Part II)

รศ.ดร. อนันต์ ผลเพิ่ม

Asso. Prof. Anan Phonphoem, Ph.D.anan.p@ku.ac.th

http://www.cpe.ku.ac.th/~anan

Computer Engineering Department

Kasetsart University, Bangkok, Thailand

Nov 2010

2

Outline

IP Fundamental Operation

Internet Protocol

Addressing

Supporting Protocol

3

IP Header

32 bits

32 bits

IP Address

Address space of IPv4 (32 bits)

232 = 4,294,967,296

Unique and Universal

Local & Global Sense

Assigned by National Registries

Subset from Internet Corporation for Assigned Names and Number (ICANN)

Does an IP address represent a machine ?

4

5

Internet Address

6

Internet Classes

Classfull Addressing

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IP Address Class

8

Amount of Networks and Hosts

9

IP address in decimal notation

27 26 25 24 23 22 21 20

1 0 0 1 1 1 1 0x x x x x x x x

158.108.2.61

10011110 01101100 00000010 00111101

128 + 16 + 8 + 4 + 2 + = 158

10

IP address practice

10011110 01101100 00100000 00010010 158.108.32.18

00001100 00011001 00000001 00010111 12.25.1.23

11001001 01111101 10001001 11010101 201.125.137.213

#1

#2

#3

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IP address in decimal notation

158.108.2.61

10011110 01101100 00000010 00111101

www.ku.ac.th

Class Ranges

12

13

IP Address Class

A50%

B25%

C12.5%

D

E

IP Address Blocks

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15

Special IP Addresses

Network Address all hosts = 0; e.g. 158.108.0.0/16

Directed Broadcast Address all hosts = 1; e.g. 158.108.255.255/16

Limited Broadcast Address all 1; e.g. 255.255.255.255

This computer Address all 0; e.g. 0.0.0.0

Loopback Address 127.0.0.0/8 127.0.0.1

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Loopback Address

โปรเซส Aโปรเซส A โปรเซส Bโปรเซส B

ทีซพี/ียูดีพี

ไอพ ี

เดทาลิงค์

ฟสิิคลั

ลูปแบ็คอินเทอรเ์ฟส

127.0.0.1

แอดเดรสอ่ืนๆ

แพก็เก็ตผา่นลูปแบ็คอินเทอรเ์ฟสเข้าสูอี่กโปรเซสหนึ่ง

แพก็เก็ตถกูส่งเข้าลูปแบ็คอินเทอรเ์ฟส

โปรเซส Aโปรเซส A โปรเซส Bโปรเซส B

ทีซพี/ียูดีพี

ไอพ ี

เดทาลิงค์

ฟสิิคลั

ลูปแบ็คอินเทอรเ์ฟส

127.0.0.1

แอดเดรสอ่ืนๆ

แพก็เก็ตผา่นลูปแบ็คอินเทอรเ์ฟสเข้าสูอี่กโปรเซสหนึ่ง

แพก็เก็ตถกูส่งเข้าลูปแบ็คอินเทอรเ์ฟส

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Broadcast Address

Ending with 255

Use for sending to all nodes in class range

Class A broadcast:

10.255.255.255

Class B broadcast:

158.108.255.255

Class C broadcast:

202.100.15.255

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Private IP Address

Class A (1 group)

10.0.0.0 – 10.255.255.255

Class B (16 groups)

172.16.0.0 – 172.31.255.255

Class C (256 groups)

192.168.0.0 – 192.168.255.255

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Network Address

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Sample internet

Network and Host addresses

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A Network with Two Levels of Hierarchy

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A Network with Three Levels of Hierarchy

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Addresses with and without Subnetting

Finding a Network Address

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Network Address

25

26

Masking (without subnet)

IP Address: 141 . 14 . 2 . 21

Binary IP Address: 1000 1101 . 0000 1110 . 0000 0010 . 0001 0101

Mask: 255 . 255 . 0 . 0

Binary Mask: 1111 1111 . 1111 1111 . 0000 0000 . 0000 0000

Network Address: 141 . 14 . 0 . 0

Binary IP Address: 1000 1101 . 0000 1110 . 0000 0000 . 0000 0000

&

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Masking (with subnet)

IP Address: 141 . 14 . 2 . 21

Binary IP Address: 1000 1101 . 0000 1110 . 0000 0010 . 0001 0101

Mask: 255 . 255 . 255 . 0

Binary Mask: 1111 1111 . 1111 1111 . 1111 1111 . 0000 0000

Network Address: 141 . 14 . 2 . 0

Binary IP Address: 1000 1101 . 0000 1110 . 0000 0010 . 0000 0000

&

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Default Mask

Class In BinaryIn Dotted-

Decimal

Using

Slash

A 11111111 00000000 00000000 00000000 255.0.0.0 /8

B 11111111 11111111 00000000 00000000 255.255.0.0 /16

C 11111111 111111111 11111111 00000000 255.255.255.0 /24

Example

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A router receives a packet with the destination

address 201.24.67.32. Show how the router finds the

network address of the packet.

SolutionClass C default mask = 255.255.255.0

67

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Subnet Design

Given a network 194.30.12.0 with 16 hosts in each subnetwork

Find the following:

The number of subnetworks

Sub-network ID / Broadcast Address

Sub-netmask

First/Last address that can be used for each subnet

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Subnet Design

Last Byte(Host ID)

192.30.12.0Class C IP address

16 Hosts 24 =16 is not enough (subnetID and broadcast) 25 = 32 total of 30 hosts 5 bits for Host and 3 bits for subnet

HostSubnet

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Subnet Design

255 255 255. . .1 1 1 0 0 0 0 0Subnet Mask

00000000 = 000100000 = 3201000000 = 6401100000 = 9610000000 = 12810100000 = 16011000000 = 19211100000 = 224

Subnet Host

255 255 255. . . 224

Subnet ID 194 30 12. . .194 30 12. . .194 30 12. . .194 30 12. . .194 30 12. . .194 30 12. . .194 30 12. . .194 30 12. . .

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Subnet Design

Subnet Subnet ID 1st Add Last Add Broadcast

0 192.30.12.0 192.30.12.1 192.30.12.30 192.30.12.31

1 192.30.12.32 192.30.12.33 192.30.12.62 192.30.12.63

2 192.30.12.64 192.30.12.65 192.30.12.94 192.30.12.95

3 192.30.12.96 192.30.12.97 192.30.12.126 192.30.12.127

4 192.30.12.128 192.30.12.129 192.30.12.158 192.30.12.159

5 192.30.12.160 192.30.12.161 192.30.12.190 192.30.12.191

6 192.30.12.192 192.30.12.193 192.30.12.222 192.30.12.223

7 192.30.12.224 192.30.12.225 192.30.12.254 192.30.12.255

Exercise

34

• Given a network

• 154.120.0.0 with requirement of 70 sub-networks

• 12.0.0.0 with requirement of 40 sub-networks

• Find the following:

• The actual number of sub-networks

• The actual number of host in each sub-network

• Sub-network ID / Broadcast Address

• Sub-netmask

• First/Last address that can be used for each subnet

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Address Mapping

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Addressing

Host Address (Host Name)

Port Number

IP Address

MAC Address (Physical Address)

iwing.cpe.ku.ac.th:80

158.108.32.52

00:04:e2:05:8a:b3

Applications5

Transport4

Network3

Data Link2

Physical1

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Node-to-node delivery

Need MAC Address to communicate between nodes

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Source-to-destination delivery

Need IP Address to route packets to destination

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Resolve Name

Domain Name System (DNS)

Address Resolution Protocol (ARP)

iwing.cpe.ku.ac.th

00:04:e2:05:8a:b3

158.108.33.66

Applications5

Transport4

Network3

Data Link2

Physical1

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Address Resolution Protocol(ARP)

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Address Resolution Protocol (ARP)

Mapped IP to MAC address

Manual configuration

Automatic process by ARP

MAC address

Ethernet 6 bytes

Token ring 2 or 6 bytes

FDDI 2 or 6 bytes

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ARP protocol

RFC 826 - Address Resolution Protocol

ARP maps any network level address (such as IP) to its corresponding data link address (such as Ethernet)

supported protocol in datalink layers, not data link layer protocol

ARP in the TCP/IP protocol stack

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441 2

3 4

ARP Protocol

ARP request

ARP request

ARP request

ARP request

I’m looking for IP

158.109.33.200

Station 1 is looking for IP 158.109.33.200

451 2

3 4

ARP Protocol

ARP response

I’m IP 158.109.33.200

My physical address is

01-12-33-3A-C2-23

ARP response

Station 3 (IP 158.109.33.200) responses

DataPreambleand SFD

Destinationaddress

Sourceaddress

Type CRC

8 bytes 6 bytes 6 bytes 2 bytes 4 bytes

Type: 0x0806

ARP Frame

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0 15 16 31

Hardware type:16 Protocol type:16

hlen:8 plen:8 ARP Operation:16

Sender MAC addr (bytes 0-3)

sender MAC addr (bytes 4-5) sender IP addr (bytes 0-1)

sender IP addr (bytes 2-3) dest MAC addr (bytes 0-1)

dest MAC addr (bytes 2-5)

dest IP addr (bytes 0-3)

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Header details

Hardware type (2 bytes): Ethernet=1 ARCNET=7, localtalk=11

Protocol type (2 bytes): IP=0x0800

hlen (1 byte): length of hardware address, Ethernet=6 bytes

plen (1 byte): length of protocol address, IP=4 bytes

ARP operation (2 bytes): ARP request = 1, ARP reply = 2

RARP request = 3, RARP reply = 4

Hardware type:16 Protocol type:16

hlen:8 plen:8 ARP Operation:16

Sender MAC addr (bytes 0-3)

sender MAC addr (bytes 4-5) sender IP addr (bytes 0-1)

sender IP addr (bytes 2-3) dest MAC addr (bytes 0-1)

dest MAC addr (bytes 2-5)

dest IP addr (bytes 0-3)

ARP Interaction

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ARP mechanisms

Each node maintains the ARP cache it first looks in the cache to find entry first

if the entry is not used for a period (~15 minutes), it is deleted.

Receive node can adds an MAC addr entry for source station in its own cache.

ARP traffic load hosts quickly add cache entries.

If all hosts on a subnet are booted at the same time? => flurry of ARP requests and reply.

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ARP as a command line

% arp -a

www.cpe.ku.ac.th (158.108.33.5) at 0:0:e8:15:cc:c

% telnet cc

:

% arp -a

router.cpe.ku.ac.th (158.108.33.1) at 0:0:c:6:13:4a

cc.cpe.ku.ac.th (158.108.33.2) at 2:60:8c:2e:b5:8b

www.cpe.ku.ac.th (158.108.33.5) at 0:0:e8:15:cc:c

entry in ARP table

more entries added

arp command

anan@cpe:~$ arp -a

fe-cpegw2-server.cpe.ku.ac.th (158.108.32.1) at 00:1e:f7:??:??:ff [ether] on eth0

delta.cpe.ku.ac.th (158.108.32.3) at 00:16:3e:??:??:00 [ether] on eth0

anan@cpe:~$ ping jabber.cpe.ku.ac.th

PING jabber.cpe.ku.ac.th (158.108.32.7) 56(84) bytes of data.

64 bytes from jabber.cpe.ku.ac.th (158.108.32.7): icmp_seq=1 ttl=64 time=0.188 ms

64 bytes from jabber.cpe.ku.ac.th (158.108.32.7): icmp_seq=2 ttl=64 time=0.232 ms

^C

anan@cpe:~$ arp -a

fe-cpegw2-server.cpe.ku.ac.th (158.108.32.1) at 00:1e:f7:??:??:ff [ether] on eth0

jabber.cpe.ku.ac.th (158.108.32.7) at 00:04:75:??:??:ca [ether] on eth0

delta.cpe.ku.ac.th (158.108.32.3) at 00:16:3e:??:??:00 [ether] on eth0

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Proxy ARP

One node answers ARP request for another: Router R answers for Y

IP: 158.108.33.2

MAC: 02:60:8c:2e:b5:8b

IP:158.108.40.1

MAC: 00:00:e8:15:cb:0c IP:158.108.33.1

MAC: 00:00:0c:06:13:4a

X to Y requestX

RY

R send 158.108.40.1 with 00:00:0c:06:13:4a

Useful when some nodes on a network cannotsupport subnet

X do not understand subnet, so it thinks thatY is on the same subnet

Router must be configured to be a proxy ARP

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RARP

Reverse ARP : map MAC to IP addr For device that can not store IP, usually

diskless workstations Need to setup server with RARP table Use the same frame format

0x0835 for Ethernet RARP request operation 0x003 = RARP request

0x004 = RARP reply

RARP can not operate across router, BOOTP is more spread