Module 01: Dynamic Host Configuration Protocol (DHCP)

Network Service -2

Why Use DHCP?

DHCP 는 TCP/IP 를 자동 구성을 사용함으로써 구성상의 불편함과 복잡함을 해소 하였다 .DHCP 는 TCP/IP 를 자동 구성을 사용함으로써 구성상의 불편함과 복잡함을 해소 하였다 .

Manual TCP/IP ConfigurationManual TCP/IP Configuration

IP addresses 를 User 가 직접 지정

잘못된 IP address 로 구성할 수 있는 가능성이 있다 .

잘못된 network 구성은 Network issues 를 초래한다

Computer 의 Network 정보의 빈번한 변경은 관리 작업의 부하를 초래

IP addresses 를 User 가 직접 지정

잘못된 IP address 로 구성할 수 있는 가능성이 있다 .

잘못된 network 구성은 Network issues 를 초래한다

Computer 의 Network 정보의 빈번한 변경은 관리 작업의 부하를 초래

Automatic TCP/IP ConfigurationAutomatic TCP/IP Configuration

IP addresses 를 자동으로 client computers 에 부여

Clients 에게 정확한 network 구성 정보를 제공한다

Client 의 Network 구성 정보를 자동으로 Update 를 제공한다 .

Network 상에 발생 할 수 있는 문제점을 제거

IP addresses 를 자동으로 client computers 에 부여

Clients 에게 정확한 network 구성 정보를 제공한다

Client 의 Network 구성 정보를 자동으로 Update 를 제공한다 .

Network 상에 발생 할 수 있는 문제점을 제거

Network Service -3

How DHCP Allocates IP Addresses

DHCP Server DHCP Server

DHCP Database

IP Address1: Leased to DHCP Client1IP Address2: Leased to DHCP Client2IP Address3: Available to be leased

IP Address1: Leased to DHCP Client1IP Address2: Leased to DHCP Client2IP Address3: Available to be leased

DHCP Client2:IP configuration

from DHCP server

DHCP Client2:IP configuration

from DHCP server

Non-DHCP Client:Static IP

configuration

Non-DHCP Client:Static IP

configuration

DHCP Client1:IP configuration

from DHCP server

DHCP Client1:IP configuration

from DHCP server

Lease Renewal

Lease Generation

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How the DHCP Lease Generation Process Works

DHCP client 가 broadcasts 로 DHCPDISCOVER packet 요청DHCP client 가 broadcasts 로 DHCPDISCOVER packet 요청11DHCP servers 는 broadcast 로 DHCPOFFER packet 응답DHCP servers 는 broadcast 로 DHCPOFFER packet 응답22DHCP client 가 broadcasts 로 DHCPREQUEST packet 요청DHCP client 가 broadcasts 로 DHCPREQUEST packet 요청33DHCP Server1 broadcasts 로 DHCPACK packet 을 응답DHCP Server1 broadcasts 로 DHCPACK packet 을 응답44

DHCP ClientDHCP Client

DHCP Server1DHCP Server1

DHCP Server2DHCP Server2

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How the DHCP Lease Renewal Process Works

DHCP ClientDHCP ClientDHCP Server1DHCP Server1

DHCP Server2DHCP Server2

DHCP Client sends a DHCPREQUEST packetDHCP Client sends a DHCPREQUEST packet11

DHCP Server1 sends a DHCPACK packetDHCP Server1 sends a DHCPACK packet22

50% of lease duration has

expired

50% of lease duration has

expired

87.5% of lease duration has

expired

87.5% of lease duration has

expired

100% of lease duration has

expired

100% of lease duration has

expired

If the client fails to renew its lease, after 50% of the lease duration has expired, then the DHCP lease renewal process will begin again after 87.5% of the lease duration has expired

If the client fails to renew its lease, after 50% of the lease duration has expired, then the DHCP lease renewal process will begin again after 87.5% of the lease duration has expired

client 가 lease time 50% 가 지나면 갱신 요청을 한다 , 만약 87.5% 의 lease time 지나도록 갱신되지 않은 경우 lease time 이 만료 된 후 , DHCP client 는 다시 IP 정보를 받기 위해 broadcasting 으로 DHCPDISCOVER 메시지를 보낸다 .

client 가 lease time 50% 가 지나면 갱신 요청을 한다 , 만약 87.5% 의 lease time 지나도록 갱신되지 않은 경우 lease time 이 만료 된 후 , DHCP client 는 다시 IP 정보를 받기 위해 broadcasting 으로 DHCPDISCOVER 메시지를 보낸다 .

DHCP ClientDHCP ClientDHCP Server1DHCP Server1

DHCP Server2DHCP Server2

DHCP client sends a DHCPREQUEST packetDHCP client sends a DHCPREQUEST packet11DHCP Server1 sends a DHCPACK packetDHCP Server1 sends a DHCPACK packet22

50% of lease duration has

expired

50% of lease duration has

expired

Network Service -6

How a DHCP Server Service Is Authorized

DomainControllerDomain

Controller

Active DirectoryActive Directory

DHCP Client DHCP Client

DHCP Server1 는 domain controller 에게 DHCP

servers 인증 요청을 한다 .

DHCP Server1 는 domain controller 에게 DHCP

servers 인증 요청을 한다 .

Unauthorized

Does not service DHCP requests

Authorized

Services DHCP requests

DHCP Server1DHCP Server1

DHCP Server2DHCP Server2

DHCP Server1 에 IP address가 존재한다면 , DHCP Client에게 IP address 를 제공할 수

있다 .

DHCP Server1 에 IP address가 존재한다면 , DHCP Client에게 IP address 를 제공할 수

있다 .

인증된 DHCP Server1 로 부터 DHCP client 는 IP address 제공

받는다 .

인증된 DHCP Server1 로 부터 DHCP client 는 IP address 제공

받는다 .

DHCP Server2 에 IP address 를 가지고 있지 않다면 , DHCP clients

는 IP address 를 Service 를 받지 못한다

DHCP Server2 에 IP address 를 가지고 있지 않다면 , DHCP clients

는 IP address 를 Service 를 받지 못한다

Active Directory domain 로부터 DHCP Server 인증을 받아야 DHCP client 들에게 DHCP Server service 를 할 수 있다Active Directory domain 로부터 DHCP Server 인증을 받아야 DHCP client 들에게 DHCP Server service 를 할 수 있다

DHCP Server2 는 domain controller 에게 DHCP Server

인증 요청을 한다 .

DHCP Server2 는 domain controller 에게 DHCP Server

인증 요청을 한다 .

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Lesson: Configuring a DHCP Scope

What Are DHCP Scopes? How to Configure a DHCP Scope

Network Service -8

What Are DHCP Scopes?

Scope( 범위 ) 란 DHCP 서비스를 사용하는 Subnet 에서 관리 목적을 위해 컴퓨터의 IP addresses 그룹으로 묶은 것입니다

Scope( 범위 ) 란 DHCP 서비스를 사용하는 Subnet 에서 관리 목적을 위해 컴퓨터의 IP addresses 그룹으로 묶은 것입니다

Scope PropertiesScope Properties Network ID Lease

duration

Scope name

Subnet mask Router Exclusion range

Network IP address range

LAN A LAN B

DHCP ServerDHCP Server

Scope BScope BScope AScope A

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Lesson: Configuring a DHCP Reservation

What Is a DHCP Reservation? How to Configure a DHCP Reservation

Network Service -10

What Is a DHCP Reservation?

Reservation 란 특정 DHCP Client 가 IP address 의 영구적인 사용에 대비하여 특정한 IP address 를 예약한 것을 말한다Reservation 란 특정 DHCP Client 가 IP address 의 영구적인 사용에 대비하여 특정한 IP address 를 예약한 것을 말한다

Subnet ASubnet A Subnet BSubnet B

Workstation 1Workstation 1

DHCP ServerDHCP ServerWorkstation 2Workstation 2

File and Print Server

File and Print Server

IP Address1: Leased to Workstation 1IP Address2: Leased to Workstation 2 IP Address3: Reserved for File and Print Server

IP Address1: Leased to Workstation 1IP Address2: Leased to Workstation 2 IP Address3: Reserved for File and Print Server

Network Service -11

Lesson: Configuring DHCP Options

What Are DHCP Options? How DHCP Server, Scope, and Reserved Client

Options Are Applied How DHCP Class-level Options Are Applied How to Configure DHCP Options

Network Service -12

What Are DHCP Options?

DHCP options 에서 configuration parameters 들은 DHCP service 가 clients 에게 IP address 와 default gateway 를 제공한다 .DHCP options 에서 configuration parameters 들은 DHCP service 가 clients 에게 IP address 와 default gateway 를 제공한다 .

DHCP ClientDHCP Client

DHCP ServerDHCP Server

DHCP Client IP Configuration DataDHCP Client IP Configuration Data

Client’s IP address

Client’s subnet mask

DHCP options such as: Router’s IP address DNS server’s IP address WINS server’s IP address DNS domain name

Client’s IP address

Client’s subnet mask

DHCP options such as: Router’s IP address DNS server’s IP address WINS server’s IP address DNS domain name

Network Service -13

How DHCP Server, Scope, and Reserved Client Options Are Applied

DHCP option applied at theserver level

DHCP option applied at theserver level

DHCP option applied at thescope level

DHCP option applied at thescope level

DHCP option applied at thereserved-client level

DHCP option applied at thereserved-client level

Scope AScope A Scope BScope B

Windows XPWindows XP

DHCP ServerDHCP ServerWindows 98Windows 98

Windows XPWindows XP

RouterRouter

File and Print Server

File and Print Server

Scope AScope A Scope BScope B

Windows XPWindows XP

DHCP ServerDHCP ServerWindows 98Windows 98

Windows XPWindows XP

RouterRouter

File and Print Server

File and Print Server

Network Service -14

How DHCP Class-level Options Are Applied

DHCP option applied at theclass level

DHCP option applied at theclass level

Scope AScope A Scope BScope B

DHCP ServerDHCP ServerWindows 98Windows 98

Windows XPWindows XP Windows XPWindows XP

RouterRouter RouterRouter

File and Print Server

File and Print Server

Network Service -15

Lesson: Configuring a DHCP Relay Agent

What Is a DHCP Relay Agent? How a DHCP Relay Agent Works How a DHCP Relay Agent Uses Hop Count How a DHCP Relay Agent Uses Boot Threshold How to Configure a DHCP Relay Agent

Network Service -16

What Is a DHCP Relay Agent?

DHCP relay agent 는 서로 다른 Subnet 에 있는 Server 와 Clinet 간에게 DHCP/BOOTP broadcasts 메시지를 relay 를 하는 작은 프로그램이다 .

DHCP relay agent 는 서로 다른 Subnet 에 있는 Server 와 Clinet 간에게 DHCP/BOOTP broadcasts 메시지를 relay 를 하는 작은 프로그램이다 .

DHCP ServerDHCP Server

ClientClient

DHCP Relay AgentDHCP Relay Agent

ClientClient ClientClient ClientClient

RoutersNon-RFC 1542

Compliant

RoutersNon-RFC 1542

Compliant

UnicastUnicast

Broadcast

Subnet A Subnet B

Broadcast

Network Service -17

How a DHCP Relay Agent Works

RouterNon-RFC 1542 Compliant

RouterNon-RFC 1542 CompliantClient1Client1

DHCP Relay AgentDHCP Relay Agent

Client2Client2

DHCP ServerDHCP Server

Client3Client3RouterNon-RFC 1542 Compliant

RouterNon-RFC 1542 CompliantClient1Client1

DHCP Relay AgentDHCP Relay Agent

Client2Client2

DHCP ServerDHCP Server

Client3Client3

Client1 broadcasts a DHCPDISCOVER packetClient1 broadcasts a DHCPDISCOVER packet11Relay agent forwards the DHCPDISCOVER message to the DHCP serverRelay agent forwards the DHCPDISCOVER message to the DHCP server22Server sends a DHCPOFFER message to the DHCP relay agentServer sends a DHCPOFFER message to the DHCP relay agent33Relay agent broadcasts the DHCPOFFER packetRelay agent broadcasts the DHCPOFFER packet44Client1 broadcasts a DHCPREQUEST packetClient1 broadcasts a DHCPREQUEST packet55Relay agent forwards the DHCPREQUEST message to the DHCP serverRelay agent forwards the DHCPREQUEST message to the DHCP server66Server sends a DHCPACK message to the DHCP relay agentServer sends a DHCPACK message to the DHCP relay agent77Relay agent broadcasts the DHCPACK packetRelay agent broadcasts the DHCPACK packet88

Network Service -18

How a DHCP Relay Agent Uses Hop Count

The hop count threshold 는 DHCP Relay Agent Packet 이 훼손 되지 않고 전달할 수 있는 routers 의 개수를 말한다 .The hop count threshold 는 DHCP Relay Agent Packet 이 훼손 되지 않고 전달할 수 있는 routers 의 개수를 말한다 .

DHCP Relay Agent 2DHCP Relay Agent 2

DHCP ServerDHCP Server

Hop Count = 2

DHCP Relay Agent 1DHCP Relay Agent 1

Network Service -19

How a DHCP Relay Agent Uses Boot Threshold

DHCP Server 2DHCP Server 2

DHCP Server 3DHCP Server 3

DHCP Relay AgentDHCP Relay Agent

Boot Threshold = 10 seconds

Local DHCP Server

Local DHCP Server

DHCP Server 2DHCP Server 2

DHCP Server 3DHCP Server 3

DHCP Relay AgentDHCP Relay Agent

Boot Threshold = 10 seconds

Local DHCP Server

Local DHCP Server

boot threshold 란 ? DHCP Client 가 Address 요청 시 얼마 후에 응답 할 것인지를 지정하는 값이다 .boot threshold 란 ? DHCP Client 가 Address 요청 시 얼마 후에 응답 할 것인지를 지정하는 값이다 .

Network Service -20

Lab : IP Addressing by Using DHCP

1. Windows 2003 Server 를 이용하여 DHCP Server 를 구성한 후 XP Client 에 Address 할당 내역을 확인한다 .

2. Cisco Router 를 이용하여 DHCP 서버를 구성하고 XP Client 에서 확인한다 .

3. 서버구성 내용1. IP Address2. Subnet Mask3. Default-Gateway4. DNS Server Address5. Domain Name6. Option 150

LAB

Network Service -21