dinh tuyen tinh (static route)(full permission).pdf

nh tuyn tnh (static route)

Copyright 2014 NTPS Training Center www.ntps.edu.vn

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Bi vit trc review mt cch tng quan v cc giao thc nh tuyn c cp ti trong chng trnh CCNA. Trong bi vit ny, chng ta s cng nhau review li k thut nh tuyn tnh (static route) ca hc phn ICND 1 ca chng trnh CCNA.

Nh chng ta bit, router thc hin vic nh tuyn da vo mt cng c gi l bng nh tuyn (routing table). Nguyn tc l mi gi tin IP khi i n router s u c tra bng nh tuyn, nu ch n ca gi tin thuc v mt entry c trong bng nh tuyn th gi tin s c chuyn i tip, nu khng, gi tin s b loi b. Bng nh tuyn trn router th hin ra rng router bit c hin nay c nhng subnet no ang tn ti trn mng m n tham gia v mun n c nhng subnet y th phi i theo ng no.

hiu r vn , ta cng xem xt v d 1:

` ```

F0/0 F0/0

S2/0 S2/0

192.168.12.0/30

192.168.1.0/24 192.168.2.0/24

.1 .2

.254 .254

R1 R2

.1 .2 .2.1

PC1 PC2 PC3 PC4

Hnh 1 S v d 1.

Trn hnh 1 l hai router i din cho hai chi nhnh khc nhau ca mt doanh nghip : R1 cho chi nhnh 1 v R2 cho chi nhnh 2. R1 s dng cng f0/0 ca n u xung mng LAN ca chi nhnh 1, mng ny s dng subnet 192.168.1.0/24. Tng t, R2 s dng cng f0/0 ca n u xung mng LAN ca chi nhnh 2, mng ny s dng subnet 192.168.2.0/24. Subnet s dng cho kt ni leased line ni gia hai chi nhnh (qua cc cng serial ca hai router) l 192.168.12.0/30.

Mc nh ban u, khi ta cha cu hnh nh tuyn trn cc router R1 v R2 th hai mng LAN ca hai chi nhnh R1 v R2 cha th i n nhau c (tc l, nu ly mt PC trong LAN 1, chng hn nh PC1 ping th n mt PC trong LAN 2, v d PC4, ping s khng thnh cng). L do ca iu ny l cc router R1 v R2 cha c thng tin v cc mng LAN ca nhau trong bng nh tuyn do khng th chuyn gi tin i n cc mng LAN ny. Ta kim tra bng cch hin th bng nh tuyn trn cc router R1 v R2.

Cu lnh hin th bng nh tuyn trn router l "show ip route" :



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Bng nh tuyn ca R1:

R1#show ip route

( b bt mt s dng)

Gateway of last resort is not set

192.168.12.0/30 is subnetted, 1 subnets

C 192.168.12.0 is directly connected, Serial2/0

C 192.168.1.0/24 is directly connected, FastEthernet0/0

Bng nh tuyn ca R2:

R2#show ip route

( b bt mt s dng)





T kt qu hin th, ta thy rng mi router ban u ch hc c thng tin v nhng subnet kt ni trc tip vi n. V d: router R1 bit rng c mng 192.168.12.0/30 kt ni trc tip vo cng serial 2/0 v mng 192.168.1.0/24 kt ni trc tip vo cng fast ethernet 0/0 ca n. Cc router hon ton khng c thng tin g v cc subnet xa, khng kt ni trc tip vi mnh. Do , gi s PC1 mun ping PC4, n s ng gi mt gi tin IP ICMP vi a ch ngun l 192.168.1.1 v ch n l 192.168.2.2. Khi gi tin ny i ln n router R1, R1 tra bng nh tuyn thy rng ch n 192.168.2.2 khng thuc v bt k subnet no m R1 c trong bng nh tuyn nn n drop b gi tin ny.

Vy hai mng 192.168.1.0/24 v 192.168.2.0/24 c th i n nhau c, cc router phi in c thng tin v hai mng ny vo trong bng nh tuyn ca mnh. C hai cch thc thc hin iu : mt l ngi qun tr t in tay cc thng tin nh tuyn tnh, hai l cc router t trao i thng tin nh tuyn vi nhau v t in cc thng tin cn thiu vo bng nh tuyn ca mnh nh tuyn ng. y ta kho st cch thc hin l nh tuyn tnh.

Vic cu hnh nh tuyn tnh trn router Cisco c thc hin bng cch s dng lnh c c php nh sau:

Router(config)#ip route destination_subnet subnetmask {IP_next_hop |

output_interface} [AD]

Trong :

destination_subnet: mng ch n.

Subnetmask: subnet mask ca mng ch.

IP_next_hop: a ch IP ca trm k tip trn ng i.

output_interface: cng ra trn router.

AD: ch s AD ca route khai bo, s dng trong trng hp c cu hnh d phng.



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C th trong v d ny:

T R1 mun i n mng 192.168.2.0/24 , ta phi i ra khi cng s2/0. th hin iu vo bng nh tuyn, ta thc hin cu hnh:

R1(config)#ip route 192.168.2.0 255.255.255.0 s2/0

Tng t, T R2 mun i n mng 192.168.1.0/24 , ta phi i ra khi cng s2/0. Cu hnh:


Sau khi cu hnh xong cc route cho cc mng 192.168.1.0/24 v 192.168.2.0/24, ta thc hin kim tra bng cch hin th bng nh tuyn trn mi router:

Bng nh tuyn ca R1:

R1#show ip route

( b bt mt s dng)





S 192.168.2.0/24 is directly connected, Serial2/0

Bng nh tuyn ca R2:

R2#show ip route

( b bt mt s dng)






Ta thy rng cc thng tin cn thiu trc y xut hin trn bng nh tuyn ca cc router R1 v R2. Cc entry mi in thm ny c k hin bi k t S u dng th hin rng cc thng tin nh tuyn ny c hc vo bng nh tuyn thng qua nh tuyn tnh ( ta cng rng cc dng m t cc mng kt ni trc tip c k hiu bi k t C connected kt ni trc tip).

Khi cc PC ch default gateway y ln cc cng u ni ca cc router, ping kim tra gia cc PC thuc hai mng LAN s thnh cng:



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Hnh 2 Ping kim tra gia PC1 v PC4 t PC1.

Bn cnh vic ch ng bng cng ra (output interface), ta cng c th ch ng trong cu lnh bng a ch IP next hop, y chnh l a ch IP ca trm k tip trn ng i n mng ch.

Trn R1:

R1(config)#ip route 192.168.2.0 255.255.255.0 192.168.12.2

Trn R2:

R2(config)#ip route 192.168.1.0 255.255.255.0 192.168.12.1

Nh ta thy trn hnh 1, t R1 mun i n mng 192.168.2.0/24 th phi i qua trm k tip l R2 c a ch IP l 192.168.12.2 v t R2 mun i n mng 192.168.1.0/24 th phi i qua trm k tip l R1 c a ch IP l 192.168.12.1.

Hai kiu cu hnh ny c tc dng nh nhau, im khc bit l route static c khai bo theo kiu output interface s c AD = 0 cn route static c khai bo theo kiu IP next hop s c AD = 1. Ngoi ra nu cng ra l mt cng multi access th ta nn s dng kiu khai bo IP next hop (vn ny s c cp v gii thch chi tit trong mt bi vit khc).

V d trn y m t mt cch c bn nht cch khai bo static route trn cc router. Tip theo, ta cng kho st mt v d khc phc tp hn, s ln ny s c 03 router:

192.168.3.0/24

192.168.12.0/24

` `

F0/0

S2/0

192.168.1.0/24

.1

.254

``

F0/0

S2/0

192.168.2.0/24

.2

.254

R2

``

F0/0

S2/1

.2

.254

R3

192.168.23.0/24

.3

R1 S2/1

Hnh 3 S v d 2.



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Yu cu t ra l cu hnh nh tuyn tnh trn cc router m bo cho mi a ch trn s thy nhau.

Tng t nh v d 1, trn mi router ta s thc hin in thng tin v cc subnet khng kt ni trc tip vo bng nh tuyn ca mi router s dng cu lnh cu hnh static route:

Trn R1:




Trn R2:



Trn R3:




Lu rng chng ta phi in y thng tin nh tuyn trn tt c cc router, v nu nh ch cn mt router no trn ng i ca gi tin b thiu route, gi tin s b drop gia ng. Chng hn, gi s ta qun cu hnh ch ng i n mng 192.168.3.0/24 trn R2. Gi tin xut pht t mng 192.168.1.0/24 i n mng 192.168.3.0/24 khi i n R1 s c chuyn tip qua cng s2/0 i tip (v iu ny c ch ra trong cu hnh nh tuyn tnh ca R1), tuy nhin khi i n R2 n s b drop b v R2 thiu thng tin ca mng 192.168.3.0/24.

Ta cng xem xt tip v d th 3 v cu hnh ng d phng trong c s dng n tham s AD trong cu lnh cu hnh:

R1 R2

S2/0 S2/0

S2/1 S2/1

F0/0 F0/0LAN 1

192.168.1.0/24LAN 2

192.168.2.0/24

192.168.12.0/30

192.168.21.0/30

.1 .2

Hnh 4 S v d 3.

Ln ny yu cu t ra nh sau: cu hnh nh tuyn tnh m bo R1 i n LAN 2 ca R2 theo ng i ra cng s2/0 l chnh, ng s2/1 l d phng, ngc li, R2 li i n LAN 1 ca R1 theo ng i ra cng s2/1 l chnh, ng s2/0 l d phng. C ngha l, R1 khi chuyn gi tin i LAN 2 ca R2 lun s dng cng ra l s2/0, khi cng s2/0 ny down th t ng chuyn ng qua s2/1, khi cng s2/0 up li, li chuyn v s dng cng s2/0. Tng t vi R2.



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thc hin yu cu ny, chng ta s dng tham s AD trong cu lnh cu hnh nh tuyn tnh. Nh ni, static route c th c hai ch s AD l 0 (khi cu hnh ch cng ra) v 1 (khi cu hnh ch next hop). Ta c th thay i cc gi tr mc nh ny phc v cho vic cu hnh d phng.

Nhc li rng AD dng so snh u tin gia cc route. Khi tn ti nhiu ng i n cng mt ch n, ng i no c ch s AD nh hn, ng i s c a vo bng nh tuyn s dng, nhng ng cn li c AD cao hn s c dng d phng cho ng chnh thc. Do ta ch vic chn AD nh hn (v d l 5) cho ng chnh v chn AD ln hn (v d l 10) cho ng ph.

Cu hnh trn R1:

R1(config)#ip route 192.168.2.0 255.255.255.0 Serial2/0 5


Cu hnh trn R2:



Ta thc hin kim tra kt qu cu hnh trn R1:

u tin, ta hin th bng nh tuyn xem ng no c a vo bng:

R1#show ip route

( b bt mt s dng)







Ta thy ng c a vo bng nh tuyn s dng c cng ra l s2/0 ng nh yu cu.

Tip theo ta th tnh d phng bng cch shutdown cng s2/0 ca R1:

R1(config)#interface s2/0

R1(config-if)#shutdown

R1(config-if)#

*Mar 1 00:15:48.971: %LINK-5-CHANGED: Interface Serial2/0, changed

state to administratively down

*Mar 1 00:15:49.971: %LINEPROTO-5-UPDOWN: Line protocol on Interface

Serial2/0, changed state to down

ng chnh khng cn, ta hin th li bng nh tuyn chc chn rng ng ph (i ra cng s2/1) c a vo bng nh tuyn:

R1#show ip route

( b bt mt s dng)






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Ta thc hin m li cng s2/0 v kim tra rng ng i qua cng ny li c a li vo bng nh tuyn s dng:

R1(config)#interface s2/0

R1(config-if)#no shutdown

R1(config-if)#

*Mar 1 00:19:36.767: %LINK-3-UPDOWN: Interface Serial2/0, changed

state to up

R1(config-if)#

*Mar 1 00:19:37.775: %LINEPROTO-5-UPDOWN: Line protocol on Interface

Serial2/0, changed state to up

R1#show ip route

( b bt mt s dng)







R1#

Thc hin kim tra tng t trn R2.

Nhn chung, nh tuyn tnh c u im l kh d hiu v cng d cu hnh. Thm na, nh tuyn tnh cn c mt u im khc l khng gy hao tn ti nguyn mng do khng c s trao i thng tin nh tuyn gia cc router. Tuy nhin nhc im ca nh tuyn tnh l hon ton khng thch hp vi nhng mng c quy m ln (ta khng th cu hnh tay khai bo cc route khi s lng ln n hng trm c!) v khng hi t vi mi s thay i trn s mng khi m cng ra vn trng thi up/up. khc phc cc nhc im ny, chng ta phi s dng nh tuyn ng bng cch chy mt giao thc nh tuyn no . Cc giao thc nh tuyn c th trong chng trnh CCNA s c review trong cc bi vit tip theo.

S v d 1S v d 2S v d 3

dinh tuyen tinh (static route)(full permission).pdf

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