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Cc kiu STP

Cc kiu STP- Trong phn 3.1 ta tm hiu hot ng ca STP lm th no ngn chn v khi phc t s thay i topolofy mng mt cch kp thi. u tin STP c pht trin hot ng trong mi trng bridge, v c bn h tr mt LAN (hoc mt VLAN). Vic thc thi STP trong mi trng switch i hi thm s thay i v cn nhc h tr cho nhiu VLAN. V vy, IEEE v Cisco tip cn STP khc nhau. Trong phn ny ta s xem li ba kiu STP truyn thng bt gp trong mng switch v n lin quan vi nhau nh th no.- Ch : IEEE b sung vo chun STP ci tin tnh leo thang v hi t. 1. Common Spanning Tree (CSP)- Chun IEEE 802.1Q ni r v lin kt trunk gia cc switch cho VLAN, v n cng ni r trng hp cho tt c VLAN. Trng hp ny c gi l Common Spanning Tree CSP. Tt c cc CST BPDU c truyn trn VLAN nh l frame khng gn th. C mt STP cho nhiu VLAN lm n gin ha cu hnh switch v gim bt ti cho CPU ca switch trong khi tnh ton STP. Tuy nhin ch c mt STP th cng c nhiu gii hn. Cc lin kt d phng gia cc switch s b kha v khng c kh nng cn bng ti, lm cho vic chuyn tip trn mt lin kt khng h tr cho tt c VLAN, trong khi cc lin kt khc th b kha.2. Per-VLAN Spanning Tree (PVSP)- Cisco c mt phin bn ring ca STP cung cp tnh mm do hn CST. Per-VLAN Spanning Tree PVST hot ng tch ri i vi mi VLAN ring. iu ny cho php STP trn mi VLAN c cu hnh c lp, cung cp kh nng hot ng tt hn v iu chnh cc iu kin r rng. Nhiu Spanning Tree cng c kh nng cn bng ti trn cc lin kt d phng khi cc lin kt ny c gn cho c VLAN khc nhau.3. Per-VLAN Spanning Tree Plus (PVSP+)- Cisco a ra phin bn th 2 ca STP l Per-VLAN Spanning Tree Plus (PVSP+) cho php cc thit b hot ng bn trong vi c PVST v CST. PVST+ h tr hiu qu ba nhm hot ng STP trong cng mng Campus:

Catalyst switch chy PCST. Catalyst switch chy PCST+. Switch chy CST trn 802.1Q.

lm c iu ny, PVST+ hot ng nh l b chuyn i gia cc nhm CST switch. PVST+ cng truyn thng trc tip vi PVST bng cch s dng ISL trunk. Tuy nhin truyn thng vi CST, PVST+ phi thay i cc BPDU v khng cn gn th cho frame qua VLAN. Cc BPDU t STP khc (VLAN khc) c truyn qua phn CST ca mng bng tunnel. PVST+ gi cc BPDU ny bng cch s dng a ch multicast duy nht cc CST switch chuyn tip n n cc ln cn downstream m cn phin dch n. Nh vy PVST+ v CST c th lm vic vi nhau. --------------------------------------------------------------------------------------STP - Spanning Tree Protocol

Xin cho hi cc khi nim chung quanh n ( nm chc). Cch xc nh Root Bridge v Root Port, Designated port v Nondesigned port (blocking).Thanks

bestirboy

10-17-2003

phieudu Member

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Re: STP - Spanning Tree Protocol

Theo mnh hiu th th nySpanning tree protocol l giao thc c dng trong switch trnh lp hay ni cch khc l theo dng cy,c 2s mi switch s gi BPDU(Bridge protocol data unit) ti switch khc ,BPDU ny bao gm bridge ID, trong Bridge ID gm 8 byte trong 2 byte u tin(prioty) c mc nh l 32768 v 6 byte cho a ch MAC, khi trao i cc BPDU ny gia cc switch n s bu ra mt root bridge da vo Bridge ID thp nht, bi v mc nh ca 2 byte u tin l 32768 nn n s da vo a ch MAC bu chn root bridge, v a ch MAC l ko th thay i cho nn i khi nh qun tr mun chn root bridge theo mnh, h s thay i 2 byte u tin . sau khi chn root bridge s tip tc chn root port da trn gi tr i ti root bridge l thp nht hay ni cch khc l i ti root bridge l nhanh nht.Designated port: tt c cc port trn root bridge l designated port, cc port trn cc switch khc l designated port da trn path cost or bridge ID, nu path cost ca cc port n root bridge l nh nhau th s da trnbridge ID la chn designate portBlocking:cc cng cn li

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10-18-2003

dauquan

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xin cho bit r hn v c ch hot ng ca spanning tree, ti khng hiu vi vic chia ra nh vy th lm th no SPT c th gip cho switch chng loop

dauquan

10-18-2003

phieudu Member

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Re: STP - Spanning Tree Protocol

bn nhn ci cy bao gi cha, root bridge c v nh ci gc ca cy vy, t gc cy i ln ra cc cnh cy ri nhnh cy, cho nn khi gi tin c lun chuyn trn mi trng switch th ch c mt ng duy nht i n ch, ko c ng th 2, blocking c to ra ko c ng th 2 ny. gi tin s ko i qua c cc port b blocking

Thn

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10-18-2003

nguyenquang Senior Member

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HYPERLINK "http://vnpro.org/forum/showthread.php?t=1351" \l "#"

n gin, SPT s Block cc Port "khng cn thit" trong mt ng Switch chng cho nhau! Trong n s cha li mt Port gn vi RootBridge nht lm Desinated Port. Ngoi ra, nhng Switch c MAC cao hn s phi lm Non-Root v ch c mt RootPort m thi, vic ny s trnh cho vic xut hin BroadCast Storm v trnh Loop v khng c chuyn d liu b truyn i v lp li nhiu ln. Tuy nhin, gia cc Port Undesinated vn nhn c Ni vui, n s trnh chuyn Mt rng c 2 cp :mrgreen:

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10-18-2003

bestirboy

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Cn 1 im ny na, l STP ch ng vi 1 Switch ang xt, nu qua switch khc th xt STP ca cc khc, bi v Root port c th l con ng ngn nht n Root Bridge ca Switch ny cha chc l con ng ngn nht n Switch khc. iu ny ng khng nh? (Ci ny mnh suy ngh da vo 1 v d t a ra).Mt mng c th c hng sa s cc Root Port, v mi khi "r nhnh" (c th hiu nh 1 ci mt ca nhnh cy) s to ra 1 Root Port.???

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10-18-2003

thanhtran Junior Member

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Re: STP - Spanning Tree Protocol

trong mng c nhiu switch ni vng vi nhau, trnh Loop ngi ta ngi ta dung STP.Nhng STP do Cisco a ra nn ch ranh loop cho switch ca Cisco,cn nhng siwtch ca hng khc phi dng 802.12q.Ngi ta xc nh Root Bridge v Non root bridge t y xc nh root port v destinated port nhm mc ch xc dnh port b lock---->ngn chn loop trong sitch.

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10-19-2003

it_email Senior Member

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Re: STP - Spanning Tree Protocol

Quote:

Originally Posted by phieudu

U sai ri!Nhng port nm trn root bridge l root port,cc port cc switch khc ni trc tip vi root bridge s nhn least BPDU message t RB v tr thnh root port, cn designated por l nhng port send less BPDU message

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10-23-2003

themask Senior Member

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Re: STP - Spanning Tree Protocol

Hi, cc bn xem file nh km.

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#10

10-30-2003

bestirboy

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Cho thm v d vi t nht l 5 Switch i, Nh hnh trn th ch c 2 Switch, vn cha r lm v theo mnh hii l th ny:

Quote:

Originally Posted by bestirboy

STP ch ng vi 1 Switch ang xt, nu qua switch khc th xt STP ca cc khc, bi v Root port c th l con ng ngn nht n Root Bridge ca Switch ny cha chc l con ng ngn nht n Switch khcMt mng c th c hng sa s cc Root Port, v mi khi "r nhnh" (c th hiu nh 1 ci mt ca nhnh cy) s to ra 1 Root Port.

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Cc trng thi ca STP

Tc gi:V Th H

1. Cc trng thi ca STP:- Sau khi bridge phn chia c cc port nh Root Port, Designated Port v non-Designated Port, th vic to ra topology cha loop-free khng phc tp lm, Root Port v Designated Port chuyn tip lu lng, trong khi non-Designated Port th kha lu lng. Vic chuyn tip v kha ch l 2 trng thi thng thng trong mng, bng 3.3 m t 5 trng thi ca STP.

- Trng thi Disable cho php ngi qun tr mng qun l vic ngng hot ng ca mt port. Sau khi khi to, cc port bt u trong trng thi Blocking lng nghe cc BPDU.- Do s a dng ca cc s kin m bridge truyn trong trng thi Listening (v d nh mt bridge ngh n l Root Bridge ngay sau khi khi ng). trng thi ny, khng c d liu ngi dng c truyn qua, tc l port ang gi v nhn cc BPDU c gng xc nh active topology. Trong trng thi Listening s dng 3 bc hi t ni trn, cc port b mt quyn Designated Port ch nh tr thnh non-Designated Port v tr li trng thi Blocking.- Cc Designated Port v Root Port sau 15s (gi tr mc nh ca b nh thi) s chuyn qua trng thi Learning. Trong khong 15s khc, bridge vn khng chuyn cc frame ca ngi dng qua, m xy dng bng bridge ca n. Khi Bridge nhn frame, n a a ch MAC v port vo bng bridge. Trng thi learning s gim bt s lng trn ngp khi vic chuyn tip d liu bt u.- Ch : Trong vic lu tr a ch MAC v thng tin port, cc Catalyst hc cc thng tin nh VLAN ngun.- Nu mt port vn l Designated Port hay Root Port khong thi gian cui ca trng thi Learning, th port chuyn qua trng thi Forwading. trng thi ny, n bt u gi v nhn cc frame ca ngi dng. Hnh 3.11 m t trng thi cc port v vic chuyn trng thi.

- Hnh 3.12 biu din mng vi s phn chia port v danh sch cc trng thi. Ch l tt c cc port u chuyn tip tr port 1/2 ca Cat-C.

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10-14-2006

thanhsang_truong Senior Member

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2. B nh thi gian STP: - Mt bridge tri qua 15s mi trng thi Listening v Learning. STP c iu khin bi ba b m thi gian (timer) nh trong bng 3.5.

- V d: gi s rng link on 3 trong hnh 3.12 s dng mt Hub v port 1/2 ca Cat-B truyn ra ngoi. Cat-C khng thng bo li lin v n vn ang nhn lin kt Ethernet t Hub. Cat-C ch thng bo l cc BPDU ngng n. Sau 20s (Max Age), th port 1/2 ca Cat-C ly thng tin BPDU c vi port 1/2 ca Cat-B l Designated Port cho on mng 3. iu ny lm cho port 1/2 ca Cat-C truyn trong trng thi Listening c gng tr thnh Designated Port. V vy Port 1/2 ca Cat-C cung cp truy cp tt nht t Root Bridge n lin kt ny, nn n chuyn sang trng thi Forwarding. Nh vy, Cat-C mt 50s (20s Max Age + 15s Listenning + 15s Forwarding) vt qua sau khi port 1/2 trn Cat-B b li.- Trong trng hp ny, cc bridge c th pht hin s thay i topolo gy mng trn cc lin kt kt ni trc tip v ngay lp tc chuyn sang trng thi Listening m khng cn ch thi gian Max Age. Xem v d trong hnh 3.13.

- Trong trng hp ny, port 1/1 ca Cat-C b li, v lin kt trn Root Port cng b li nn ngay lp tc port 1/2 ca Cat-C chuyn sang trng thi Learning tr thnh Root Port mi thay v ch 20s ri mi ly thng tin c. iu ny lm cho thi gian hi t STP gim t 50s xung 30s (15s Listening + 14s Learning).- Ch : thi gian hi t STP l t 30s n 50s. - Hai im quan trng cn nh khi s dng b nh thi STP l:

Th nht: khng thay i gi tr thi gian mc nh khi khng c s cn nhc cn thn. Th hai: ta ch c sa thi gian t Root Bridge.

3. Hai loi BPDU:- C hai loi BPDU l :

BPDU cu hnh. BPDU thng bo thay i topology mng TCN BPDU (Topology Change Notification BPDU).

- BPDU cu hnh c bt u bi Root Bridge v pht ra trn cc con ng hot ng t Root Bridge, cn TCN BPDU hng v Root Bridge cnh bo vi Root Bridge l topology mng c s thay i.BPDU cu hnh : cc trng trong BPDU cu hnh c tm tt trong bng 3.6

TCN BPDU (Topology Change Notification BPDU) : - TCN BPDU n gin hn BPDU cu hnh v ch gm c ba trng. TCN BPDU ging nh ba trng u tin ca BPDU cu hnh nhng trng Type th thay i vi gi tr nh sau :

0x00 (0000 0000): BPDU cu hnh. 0x80 (1000 0000): TCN BPDU.

- Ch : TCN BPDU khng mang bt c thng tin b sung no.

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