BM MMT&VT Khoa CNTT Trng H KHTN TPHCM Trang 1
Minh ho phn tch gi tin giao thc DHCP
Mc Tiu:
Bi hng dn ny gip sinh vin c th:
Nhc li c ch hot ng ca giao thc DHCP
S dng cng c wireshark bt gi tin v phn tch hot ng ca mt
giao thc
I. Nhc li dch v DHCP l g
I.1.DHCP l g?
Dynamic Host Configuration Protocol (DHCP) l mt giao thc hot ng
tng ng dng, cho php cu hnh a ch IP ca cc my trm mt cch t ng. T
c th qun l tp trung a ch IP ca cc my trong mt mng ni b hn ch c
xung t c th xy ra cng nh d dng cp nht cc thay i c th c v a ch IP
ca cng ty.
DHCP hot ng nh mt phn m rng ca giao thc BOOTP. Ngoi vic cung cp
kh nng cu hnh IP cho cc my con, DHCP cn cho php ngi qun tr thit lp cc
trng khc nh DNS server hay WINS server.
BM MMT&VT Khoa CNTT Trng H KHTN TPHCM Trang 2
I.2.C ch hot ng
Qu trnh hot ng ca giao thc DHCP c m t gm 4 bc sau y :
II. Phn tch qu trnh hot ng ca DHCP
II.1.Chun b :
Chng trnh Vmware tt dch v DHCP
Hai my o : client v server (c hai my o u dng card mng host-only; my server
ci h iu hnh Windows server 2003) kt ni vi nhau theo s bn di
Ci t dch v DHCP trn my server v cu hnh cp pht a ch cho mt lp mng
192.168.1.0/24, khong cp pht nm trong khong t 192.168.1.10/24 -
192.168.1.100/24 theo m hnh sau vi xx = 01:
DHCP server
192.168.xx.254/24
192.168.xx.0/24
DHCP client
Host-only Host-only
1. Ci t Wireshark trn my client.
2. Cu hnh cho my client nhn IP ng.
BM MMT&VT Khoa CNTT Trng H KHTN TPHCM Trang 3
II.2.Tin hnh bt gi tin trn my client theo cc bc sau :
1. M ca s Windows Command Prompt ( Start Run cmd ) v g lnh
ipconfig /release.
2. Khi ng qu trnh bt gi tin ca Wireshark.
3. Quay li ca s Windows Command Prompt g lnh ipconfig /renew.
4. i n khi lnh ipconfig /renew kt thc, g lnh ipconfig /renew mt ln
na.
5. i n khi lnh ipconfig /renew th hai kt thc, g lnh ipconfig /release
mt ln na.
6. Cui cng, thc hin li lnh ipconfig /renew ln th ba.
7. Kt thc qu trnh bt gi tin ca Wireshark.
II.3.Bt cc gi tin vi Wireshark :
S dng Wireshark bt cc gi tin theo cc bc trn, ta s thu c rt nhiu
cc gi tin thuc cc giao thc khc nhau, khng ch l cc gi tin ca DHCP. V mi
khi my nhn c mt a ch IP mi, n thng pht sinh km theo cc gi tin
thng bo cho cc my khc s tn ti ca mnh trong mng.
Ta ch quan tm n giao thc DHCP v vy cn phi tin hnh lc cc gi tin
dng ny. DHCP s dng da trn giao thc BOOTP nn ta nhp tn giao thc ny vo
ca s Filter.
BM MMT&VT Khoa CNTT Trng H KHTN TPHCM Trang 4
Cu hi 1 : DHCP s dng giao thc no cho tng vn chuyn ?
V mt lch s DHCP xy dng da trn giao thc BOOTP s dng giao thc
UDP cho tng vn chuyn. Ta c th thy r iu ny khi khng thy cc bt tay ba
bc ca giao thc TCP trn cc gi tin bt c.
Kim tra vi cc gi tin bt c bng Wireshark, ta thy mc Internet Protocal
s dng UDP.
BM MMT&VT Khoa CNTT Trng H KHTN TPHCM Trang 5
Cu hi 2 : V th thi gian th hin th t ca 4 gi tin DHCP :
Client Server -192.168.1.254/24
DHCP DISCOVER
DHCP OFFER
DHCP REQUEST
DHCP ACK
Port 67 Port 68
Cu hi 3 : ia ch tng Datalink ca my Client l g :
Ta s coi a ch Mac ca my client phn Ethernet II thu c a ch sau:
MAC = 00:0c:29:5b:ef:6a
BM MMT&VT Khoa CNTT Trng H KHTN TPHCM Trang 6
Cu hi 4 : a ch ngun v ch ca cc gi tin :
DHCP DISCOVER
Source IP : 0.0.0.0
Destination IP : 255.255.255.255
DHCP OFFER
Source IP : 192.168.1.254
Destination IP : 255.255.255.255
DHCP REQUEST
Source IP : 0.0.0.0
Destination IP : 255.255.255.255
DHCP ACK
Source IP : 192.168.1.254
Destination IP : 255.255.255.255
Cu hi 5 : Gi tin no ch a ch IP m Server mun cp cho my client :
Ta c th thy gi DHCP OFFER m my DHCP server gi cho client cha cc
thng tin v a ch IP ca client cng nh cc phn ph thm nh Subnet mask, DNS IP
BM MMT&VT Khoa CNTT Trng H KHTN TPHCM Trang 7
I.
Gi tin trn cha cc thng tin c bn sau :
a ch IP Client 192.168.1.10
Subnet Mask 255.255.255.0
DHCP Server 192.168.1.254
DNS Server 8.8.8.8
Lease Time 8 days
Cu hi 6 : a ch IP m Client mun DHCP cp trong gi DHCP REQUEST :
BM MMT&VT Khoa CNTT Trng H KHTN TPHCM Trang 8
Sau khi nhn c thng tin v a ch IP DHCP Server mong mun cp ti gi
DHCP OFFER. Client s xc nhn n mun nhn a ch IP no gi tin DHCP
REQUEST.
y a ch l: 192.168.1.10.
Cu hi 7 : Gi tin no ch a ch IP m Server s cp cho Client :
y l gi cui cng, xc ch cc thng tin tha thun gia Server v Client
trong sut qu trnh trao i cng nh l gi tin cui cng trong qu trnh giao tip
DHCP c tn gi DHCP ACK.
BM MMT&VT Khoa CNTT Trng H KHTN TPHCM Trang 9
Ti liu tham kho
http://www.wikipedia.org/
http://technet.microsoft.com/
http://www.nhatnghe.com/
Top Related