Dhcp Server Ubuntu

MC LC

LI NI U ................................................................................................................. 2

CHNG 1: GII THIU V DHCP ........................................................................... 3

1.1. DHCP l g? .......................................................................................................... 3

1.2. ngha ca vic s dng DHCP. ......................................................................... 3

1.3. Mt s thut ng c dng trong DHCP. .......................................................... 4

1.4. C ch xin v cp pht IP Address cho DHCP Client ca DHCP Server. ........... 4

1.5. C ch t ng refrest li thi gian ng k (lease time). ................................... 6

1.6. u im ca DHCP .............................................................................................. 6

CHNG 2: TRIN KHAI DHCP SERVER TRN UBUNTU SERVER .................. 8

2.1. Chun b trc khi tin hnh trin khai ................................................................ 8

2.2. Trin khai cu hnh ............................................................................................... 8

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Nghin cu trin khai DHCP Server trn Ubuntu Server

LI NI U

Ngy nay, cng ngh thng tin tr nn ph bin v m bo tnh hiu qu cho

hot ng sn xut, kinh doanh ca cc doanh nghip. i lin vi l s i hi v

kh nng p ng v cng ngh thng tin ni chung v s thng sut ca h tng mng

ni ring.

S pht trin ca Internet cng ng ngha vi vic tng trng v quy m v

cng ngh nhiu mng LAN, WAN, Chnh iu lm cho vn s dng vi

tnh cng tng v vi quy m ln. Do , vn d qun l v cu hnh tr nn quan

trng hn bao gi ht. Vic thit k mng v cp pht a ch IP t ng sao cho nhanh

chng, tit kim thi gian v cng sc, ti nguyn ca t chc l vn ng quan

tm. Internet pht trin cng mnh, lng ngi truy cp cng tng, nhu cu s dng

vi tnh cng nhiu th ngi qun tr mng cng phi tn nhiu cng sc bo tr,

qun l, m rng kh khn hn.

Dynamic Host Configuration Protocol (DHCP) l giao thc cu hnh a ch IP

ng, l dch v trn nn giao thc TCP/IP nhm n gin ha vai tr qun tr ca vic

cu hnh a ch IP ca mng Client.

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CHNG 1: GII THIU V DHCP

1.1. DHCP l g?

DHCP l vit tt ca Dynamic Host Configuration Protocol l giao thc cu

hnh a ch IP ng, l phn m rng ca BootProtocol, DHCP c nhim v l cp

pht a ch IP ng cho cc Client.

My tnh c cu hnh mt cch t ng v th vic s dng DHCP s gim

vic can thip vo h thng mng. N cung cp mt database trung tm theo di tt

c cc my tnh trong h thng mng. Mc ch quan trng nht l trnh trng hp

hai my tnh khc nhau li c cng a ch IP.

DHCP bn cht l mt dch v c s h tng c trn bt k mt h thng mng

no nhm cung cp a ch IP v thng tin DNS server ti cc PC client hay mt s

thit b khc.

1.2. ngha ca vic s dng DHCP.

DHCP c s dng gip bn khng phi n nh a ch IP tnh cho tt c

cc thit b c trong h thng mng ca mnh v gip bn qun l mi vn m a

ch IP tnh c th to ra.

Thng thng trong mt m hnh mng, ngi qun tr c th cu hnh IP cho

cc my client theo hai cch l th cng (static) v cp pht ng (dynamic). Vi cc

h thng mng nh static c th p ng c nhu cu y, nhng vi cc mng ln th

vic cp pht IP mt cch t ng l thit yu hn c v DHCP ra i p ng nhu cu

y.

DHCP cho php cc nh qun tr mng c th t mt trung tm qun l v t

ng m ha qu trnh gn IP cc thng s cho mt mng my tnh trong mt khong

thi gian nht nh.

Tt c vic trao i thng tin gia mt DHCP server v DHCP client s s dng

User Datagram Protocol (UDP) port l 67 v 68.

Ngoi vic cung cp a ch IP, DHCP cn cung cp thng tin cu hnh khc, c

th nh DNS. Hin nay DHCP c 2 version: cho IPv4 v IPv6.

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1.3. Mt s thut ng c dng trong DHCP.

DHCP client My trm DHCP: l mt thit b ni vo mng v s dng giao

thc DHCP ly cc thng tin cu hnh nh l a ch mng, a ch my ch

DNS.

DHCP server My ch DHCP: l mt thit b ni vo mng c chc nng tr

v cc thng tin cn thit cho my trm DHCP khi c yu cu.

BOOTP relay agents Thit b chuyn tip BOOTP: l mt my trm hoc mt

router c kh nng chuyn cc thng ip DHCP gia DHCP server v DHCP

client.

Binding Ni kt: l mt tp hp cc thng tin cu hnh trong c t nht mt

a ch IP, c s dng bi mt DHCP client. Cc ni kt c qun l bi

my ch DHCP.

1.4. C ch xin v cp pht IP Address cho DHCP Client ca DHCP Server.

Giao thc DHCP lm vic theo m hnh client/server, do quy trnh cp pht

IP cho client c thc hin qua bn bc sau:

IP lease request

IP lease offer

IP lease selection

IP lease acknowledgement

1.4.1. IP Lease Request

u tin t DHCP client s broadcast mt message tn l DHCP discover. V

lc ny client cha c a ch IP nn n s c source l 0.0.0.0 v cng khng bit

c ch n l server no nn n s gi 1 tin broadcast ln ton mng. Gi tin ny

bao gm c a ch MAC DHCP server c th bit c client no gi yu cu

n.

1.4.2. IP Lease Offer

Nu c mt DHCP server nhn c gi tin DHCPDISCOVER ca client th

n s tr li li bng mt gi tin DHCPOFFER, gi tin ny i km theo nhng thng

tin sau:

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MAC address ca client

IP address cp cho (offer IP address)

Mt subnet mask

Thi gian thu

a ch IP ca DHCP cp IP cho client ny

Lc ny DHCP server s c gi li mt IP offer (cp) cho client n

khng cp cho DHCP client no khc.

DHCP client ch mt vi giy cho mt offer, nu n khng nhn mt offer n s

rebroadcast (broadcast gi DHCPDISCOVER) trong khong thi gian l 2,4,8 v 16

giy.

Nu DHCP client khng nhn mt offer sau bn ln yu cu, n s dng mt

a ch IP trong khong [169.254.0.1 n 169.254.255.254] vi subnet mask l

[255.255.0.0]. N s s dng trong mt s trong khong IP v vic s gip cc

DHCP client trong mt mng khng c DHCP server thy nhau. DHCP client tip tc

c gng tm kim mt DHCP server sau mi 5 pht.

1.4.3. IP Lease Selection

DHCP client nhn c DHCP offer. N s phn hi broadcast li mt gi tin

DHCP request chp nhn ci offer . DHCP request bao gm cc thng tin v

DHCP cp a ch cho n. y DHCP client gi DHCP request nh mt thng bo

tm thy v chp nhn thu mt a ch IP t con DHCP server v thi khng cho

cc DHCP server khc gi cc DHCP offer trong trng hp h thng mng c nhiu

hn mt DHCP server.

1.4.4. IP Lease Acknowledgement

Khi DHCP server nhn c DHCP request s tr li DHCP client mt DHCP

ACK or NACK. cho bit l chp nhn cho DHCP client thu a ch IP. Gi

tin ny s bao gm a ch IP v cc thng tin cu hnh khc (DNS server, WINS

server, default getway). Khi DHCP client nhn c DHCP ACK or NACK th

chnh thc kt thc qu trnh xin, tm kim a ch IP ca DHCP client.

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Lu : Quy trnh xin, cp pht IP gia DHCP Client v DHCP Server tn hiu

truyn i l tn hiu Broadcast.

1.5. C ch t ng refrest li thi gian ng k (lease time).

Theo mc nh ca DHCP server th mi IP lease ch c c 8 ngy. Nu theo

nh mc nh (8 ngy) th mt DHCP client sau mt khong thi gian l 50% (tc l 4

ngy) n s t ng xin li IP address vi DHCP m n xin ban u. DHCP client

lc ny s gi mt DHCPREQUEST trc tip (unicast) n DHCP server m n xin

ban u.

Nu m DHCP server cn sng, n s gi li gi tin DHCPACK renew

ti DHCP client, gi ny bao gm thng s cu hnh mi cp nht nht trn DHCP

server.

Nu DHCP server cht th DHCP client s tip tc s dng cu hnh hin

thi ca n. V nu sau 87,5% (7 ngy) ca thi gian thu hin thi ca n, n s

broadcast mt DHCPDISCOVER update a ch IP ca n. Vo lc ny, n khng

tm ti DHCP server ban u cho n thu na m n l s chp nhn bt c mt DHCP

server no khc.

Nu thi gian lease ht, th client s ngay lp tc dng li vic s dng IP

address lease . V DHCP client sau s bt u tin trnh thu mt a ch nh ban

u.

Lu : Khi khi ng (restart) li DHCP client thi n s t ng renew li IP

address m trc khi n shutdown.

1.6. u im ca DHCP

1.6.1. Qun l TCP/IP tp trung

Thay v phi qun l a ch IP v cc tham s TCP/IP khc vo mt cun s

no (y l vic m qun tr mng phi lm khi cu hnh TCP/IP bng tay) th

DHCP server s qun l tp trung trn giao din ca n. Gip cc nh qun tr va d

qun l, cu hnh, khc phc khi c li xy ra trn cc my trm.

1.6.2. Gim gnh nng cho cc nh qun tr h thng

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Trc y cc nh qun tr mng thng phi nh cu hnh IP bng tay (gi l

IP tnh) nhng nay nh c DHCP server n s cp IP mt cch t ng cho cc my

trm. Nht l trong mi trng mng ln th s cn thit v hu ch ca dch v mng

ny mi thy r rng nht.

Vi kiu cu hnh bng tay th ngi dng c th thay i IP. Ngi th ty my

thch vc chi, c ngi thay i lung tung DNS server sau qun khng nh IP ca

DNS server l g t li cho ng li vi qun tr mng, c ngi t IP lm trng

vi IP ca ngi khc, ngi khc t IP trng vi Defaul Gateway ... lm cho qun tr

mng khn kh. Nhng kiu ny khng c IP ng. Ngi no thch thay i cng

chu. Ch c ngi qun tr DHCP server h mi c quyn thay i.

1.6.3. Gip h thng mng lun c duy tr n nh

a ch IP cp pht ng cho cc my trm ly t di IP cu hnh sn trn

DHCP server. Cc tham s (DG, DNS server ...) cng cp cho tt c cc my trm l

chnh xc. S trng lp IP khng bao gi xy ra. Cc my trm lun lun c mt cu

hnh TCP/IP chun. Lm cho h thng hot ng lin tc, va gim gnh nng cho

ngi qun tr va tng hiu qu lm vic cho user ni ring v doanh nghip ni

chung.

1.6.4. Linh hot v kh nng m rng

Ngi qun tr c th thay i cu hnh IP mt cch d dng khi c s h tng

mng thay i. Do lm tng s linh hot cho ngi qun tr mng. Ngoi ra DHCP

ph hp t mng nh n mng ln. N c th phc v 10 my khch cho n hng

ngn my khch.

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CHNG 2: TRIN KHAI DHCP SERVER TRN UBUNTU SERVER

2.1. Chun b trc khi tin hnh trin khai

Chng trnh chy my o VMware 9.0.1

DHCP server: Ubuntu server 13.04 trn my o VMware

DHCP client: trn my o VMware: Windows XP, Ubuntu desktop 13.04, my

tht: Windows 8.1

2.2. Trin khai cu hnh

2.2.1. Trn Ubuntu Server

Bc 1: Ci t dch v DHCP server

# apt-get install isc-dhcp-server

Bc 2: t IP tnh cho cng eth0

# nano /etc/network/interfaces

Bc 3: Ch nh card mng eth0 dng cho isc-dhcp-server

# nano /etc/default/isc-dhcp-server

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Bc 4.1: Cu hnh DHCP Server cp IP theo di mng

# nano /etc/dhcp/dhcpd.conf

Dng 1-2: Mc nh Client c cp v s dng IP trong vng 600s ti a l

7200s;

Dng 3: Ghi li log trong qu trnh hot ng;

Dng 4: Subnet v netmask ca mng;

Dng 5: Di IP s cp cho Client t 172.16.1.10 n 172.16.1.20;

Dng 6: a ch broadcast ca mng;

Dng 7: Tn ca min l mangmaytinhk54.com;

Dng 8: Full name ca server l srv1.mangmaytinhk54.com;

Dng 9: a ch Routes hay Gateway ca mng;

Bc 4.2: Cu hnh DHCP cp IP tnh theo a ch MAC

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Dng 1: Hostname ca Client

Dng 2: a ch MAC ca Client

Dng 3: Quy nh DHCP Server cp cho Client IP duy nht l 172.16.1.111

Bc 5: Khi ng li dch v DHCP server:

# service isc-dhcp-server restart

2.2.2. Trn VMware

t li ch mng cho cc my o cng mt mng.

y t c 3 my mng VMnet5.

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2.2.3. Trn Client Windows XP (VMware)

Bc 1: Cu hnh nhn IP ng t DHCP server

Bc 2: Vo Start \ Run g cmd

Bc 3: Gii phng a ch IP c ca Windows XP, dng lnh:

ipconfig /release

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Bc 4: Xin cp li a ch IP cho Windows XP, dng lnh:

ipconfig /renew

Kt qu Windows XP nhn IP t DHCP server trn Ubuntu server theo cch cu hnh

cp IP theo di mng:

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2.2.4. Trn Client Ubuntu Desktop (VMware)

Bc 1: Vo Terminal

Bc 2: Cu hnh cho my nhn IP ng:

nano /etc/network/interfaces

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Bc 3: Xin cp li a ch IP cho Ubuntu Desktop

# ifdown eth0

# ifup eth0

Kt qu Ubuntu Desktop nhn IP t DHCP Server trn Ubuntu server theo cch cu

hnh IP tnh theo a ch MAC:

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2.2.5. Trn my tht Windows 8.1

Bc 1: Vo Control Panel \ Network and Sharing Center \ Change adapter settings

Bc 2: Disable cc card mng ch gi li card VMnet1

Bc 3: Cu hnh nhn a ch IP ng ca card VMnet1

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Bc 4: Vo VMware chuyn card mng ca Ubuntu server thnh VMnet1

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Bc 5: Tt DHCP ca mng VMnet1

Bc 6: T Windows 8.1, xin cp li IP t DHCP server

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Dhcp Server Ubuntu