a ch mngBi:

Khoa CNTT HSP KT Hng Yn

a ch IP v Subnetmask

Kin thc v a ch IP v cc kin thc lin quan n M hnh TCP/IP, Subneting c trang b ti Module Mng c bn, y l mt khi kin thc nn tng rt quantrng, sinh vin cn xem li ti liu hc. n tp li khi kin thc ny sinh vincn hon tt bi tp sau:.

H thng mng ca cng ty ABC nh hnh v, cng ty c cp pht di a ch192.168.0.0/16. Thc hin chia di a ch trn thnh cc Subnet tho mn iu kin shost trong mi Subnet nh trn hnh vi iu kin ti u ho khng gian a ch IP.

Cc loi a ch IP

a ch IP Private, IP Public

IP private l nhng IP khng c nh tuyn trn Internet, bao gm cc di a ch sau:

10.0.0.0 --> 10.255.255.255

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172.16.0.0 --> 172.16.31.255

192.168.0.0 --> 192.168.255.255

Cc di a ch IP cn li ca lp A, B, C l nhng a ch IP Public (thuc quyn shu ca ISP v nh cung cp a ch Internet)

a ch IP Unicast, Multicast, Broadcast

a ch Broadcast l a ch qung b cho mt Subnet theo chiu t PC n tt c ccPC trong cng Subnet : PC-> all PC

a ch Unicast l a ch cho php gi t mt a ch n mt a ch khc :

PC->PC

a ch Multicast l a ch cho php gi t mt host n mt nhm host khc: PC->Group PC, cc a ch ny thuc lp D.

Nguyn l dch chuyn a ch IP (NAT)

Cc thut ng trong NAT

Khi mt my thc hin NAT s c c 2 chiu out v in theo quy nh ca Interface

- Cisco s dngthut ng 2 chiu ny ca NAT gi l inside v outside, cc nhm ach trong NAT bao gm:

+ Inside local: nhm a ch bn trong

+ Inside global: a ch ton cc bn trong (a ch ny i din cho cc host ca bnkt ni ra ngoi Internet, chnh l a ch m ISP cp cho bn)

+ Outside local address : l a ch ring ca host bn ngoi mng ni b

+ Outside global address: l a ch public ca host bn ngoi (vd www.yahoo.com)khi host bn trong thc hin NAT chuyn i IP, qu trnh NAT nh sau:

inside local ip address ----- inside global ip address ----- outside global ip address

vd: 192.168.1.2 ----- 58.187.41.17:2412 ------- 209.191.93.52

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Chng hn, khi vo trang web www.yahoo.com, u tin s c mt request ti webserver yahoo, y chnh l thc hin NAT outside, khi bn nhn c reply t Yahooserver, qu trnh ngc li, lc ny chnh l thc hin NAT inside

NAT inside ngc li vi NAT outside, khi gi d liu n c thit b thc hin NAT,n xem trong bng NAT (NAT table) v thy rng 58.187.41.17:2412 tng ng vi192.168.1.2, lc NAT s thc hin i li a ch IP ca gi tin v gi d liu sn c ng a ch ca my trong LAN ca bn.

Hon ton tng t nh vy vi inbound v outbound (ch khc n l thut ng caMicrosoft), nu c dng ch s port trong qu trnh chuyn i th l PAT, cn chdng a ch IP th lc chuyn i l NAT

Cu lnh net use thng dng map share trong mng lan (tuy vy bn c th mapmt my khc qua Internet, nu my php share nh vy - chng hn NAT htport v cho php ht cc service), kt ni trong Lan, hay kt ni qua Internet u c ththc hin ging nhau, qua Internet th ch b hn ch bi tc v cht lng, thng lchm hn nhiu so vi mng LAN, tuy vy t ai dng lnh net use map mt share tngoi Internet, thng dng cc cng c khc, nh l FTP, HTTP... v cc cng c chias qua Internet.

Cc kiu NAT

C 2 kiu NAT c bn l NAT v PAT :

Ging nhau

Dng chuyn i a ch IP private thnh a ch IP public, gip cho my trong mngLan ca bn c th kt ni vi Internet, v gip tit kim khng gian ca a ch IPpublic, mt cty c th ch cn 1 hay vi a ch IP public m vn cho php ton b mngca h kt ni ra th gii bn ngoi.Khc nhau :

NAT : Network Address Translation : chuyn i a ch IP thnh a ch bn ngoi(c 2 dng chuyn i l 1-1 : static, v chuyn i overload, khi bn c cp nhiu IPt ISP)

V d: chuyn i 1-1 l : 192.168.0.1 186.15.4.2, cn chuyn i overload thmt a ch bn trong s c chuyn i thnh mt a ch bn ngoi (nu nh a chbn ngoi cha s dng)

PAT (Port Address Translation), thng l cc router ADSL mc nh dng kiuchuyn i ny, v ban ch c 1 IP public, nu ton b LAN ca bn u mun kt nira ngoi - vi mt a ch IP public (58.187.168.41)=> lc a ch bn trong s cchuyn i thnh a ch kt hp vi ch s port, nu port cha s dng

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V d: Bn c mt LAN nh vi di IP : 192.168.1.x , khi cc my trong lan s cchuyn i chng hn vi vi my:

192.168.1.3 58.187.168.41:2413

192.168.1.4 58.187.168.41:2414

192.168.1.5 58.187.168.41:2415

192.168.1.6 58.187.168.41:2416

....

Cc ch s port thng dng t 1024 n 65535 (not well-known port), v well-knownport l ch yu dng cho server, s port ny p ng c hu ht cc mng LAN.

Nguyn l thu nhn mt a ch IP t DHCP Server.

C hai cch mt host c th thu nhn c mt a ch IP, ngi s dng c th cuhnh TCP/IP bng tay bng cch t nhp vo cc thng s, cch th 2 thng c sdng trong cc cng ty v cc nhn vin vng phng thng khng th nh c cc cons do ngi qun tr h thng mng trong cng ty cung cp. host c th thu nhn tng mt IP t Server, bn phi ci t dch v DHCP trn my ch. Client v Servers m phn vi nhau cp mt IP cho Client theo s sau:

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a ch mnga ch IP v SubnetmaskCc loi a ch IPa ch IP Private, IP Publica ch IP Unicast, Multicast, Broadcast

Nguyn l dch chuyn a ch IP (NAT)Cc thut ng trong NATCc kiu NAT

Nguyn l thu nhn mt a ch IP t DHCP Server.