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
#2
10-17-2003
phieudu Member
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Join Date: May 2003
Posts: 86
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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#3
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
#4
10-18-2003
phieudu Member
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Join Date: May 2003
Posts: 86
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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#5
10-18-2003
nguyenquang Senior Member
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Posts: 358
HYPERLINK "http://vnpro.org/forum/showthread.php?t=1351" \l
"#"
HYPERLINK "http://vnpro.org/forum/showthread.php?t=1351" \l
"#"
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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#6
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.???
bestirboy
#7
10-18-2003
thanhtran Junior Member
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Join Date: Sep 2003
Posts: 23
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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#8
10-19-2003
it_email Senior Member
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Join Date: Apr 2003
Location: HCM
Posts: 206
Re: STP - Spanning Tree Protocol
Quote:
Originally Posted by phieudu
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
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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#9
10-23-2003
themask Senior Member
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Join Date: Jul 2003
Posts: 143
Re: STP - Spanning Tree Protocol
Hi, cc bn xem file nh km.
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#10
10-30-2003
bestirboy
Posts: n/a
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.
==========================================================
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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#2
10-14-2006
thanhsang_truong Senior Member
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Join Date: Dec 2005
Posts: 292
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.
