CCNP3v4_Mod03 SPT Day 1.4 Ver 2

8/18/2019 CCNP3v4_Mod03 SPT Day 1.4 Ver 2

1/80

Spanning Tree Protocol


2/80

Objectives

• Define the Spanning Tree Protocol

• Maintain and Configure STP

• Configure Portfast and BPDU Guard

• Configure UplinkFast and BackboneFast

• Configure EtherChannel


3/80

Overview

• This odule introduces the fundaentals ofSpanning Tree Protocol !STP" operation in a

s#itched net#ork$

• This odule #ill also e%plain the root bridge electionprocess$

• Spanning Tree enhanceents of PortFast&UplinkFast and BackboneFast #ill also be co'ered$

• (e #ill also co'er ho# EtherChannel is configuredand ho# it interoperates #ith STP$


4/80

Transparent Bridges

• B) definition& a transparent bridge has thesecharacteristics*

+ ,t ust not odif) the fraes that are for#arded$

+ ,t learns addresses b) -listening- on a port for the sourceaddress of a de'ice$ The source M.C address is learnedinbound on a s#itchport and associated #ith that port inthe s#itch/s M.C address table$

+ ,t ust for#ard all broadcasts out all ports& e%cept for theport that initiall) recei'ed the broadcast$

+ ,f a destination address is unkno#n to the bridge& itfor#ards the frae out all ports e%cept for the port thatinitiall) recei'ed the frae$ This is kno#n as unicastflooding$


5/80

Transparent Bridges

• Transparent bridging& b) definition& ust betransparent to the de'ices on the net#ork$

• End stations re0uire no configuration$


6/80

Identifying Traffic Loops

Switch

1

Switch

2

Station A sends a frame to Station B.Both Switch 1 and 2 receive this frame, populate their MAC

addr. tables and forward the frame

Both switches forward the frame to Station B and

both switches receive the frame from the other switch.

This will cause Station A to appear as if it is connected to

Switch1 on Segment B.


7/80

Identifying Traffic Loops (cont.)

Switch

1

Switch

2

As with the previous slide, when Station Besponds to Station A, Station B will appear

As if it were connected to Switch2 on Segment A

!f station A, or an" station, sends a broadcast, the

effects of the #a"er 2 loop would be much worse.


8/80

Preventing Loops in a Layer 2 etwor!

• . loop free net#ork is one in #hich no 1a)er 2 loops e%ist$ + STP resol'es this proble

+ The 3et#ork cannot create la)er 2 broadcast stors orflooded unicast stors$

•STP allo#s for an alternate ph)sical path through the net#ork#ith creating redundant local paths$

• To achie'e this& STP allo#s onl) one of the ph)sical links to bein for#arding state #hile all other redundant paths are inblocking4discarding state$


9/80

STP "isables#Bloc!s t$e %ed&ndant Lin!

The spanning$tree algorithm %STA& runs

on each switch to activate or bloc' redundant lin's.


10/80

'2." Spanning Tree Protocol

• The 562$7D Spanning Tree Protocol !STP" pro'ides aechanis for s#itches to reconfigure the paths o'er

#hich the) for#ard fraes$

+ This #ill pro'ide a loop8free path #hen there are

redundant s#itch paths through the net#ork$


11/80

*orwarding Port and Bloc!ing Port

• . loop8free topolog) is accoplished b) for#arding traffic o'er specific portsand b) disabling other ports to a'oid fraes fro being sent repeatedl) or in aloop$


12/80

Spanning Tree +ec$anis,s

• STP is ipleented through the e%change of BPDUessages bet#een ad9acent s#itches$

• . single -root bridge- is elected to ser'e as thereference point fro #hich a loop free topolog) is

built for all s#itches e%changing BPDUs$

• Each s#itch deterines a -root port- that pro'idesthe best path to the root bridge$

• Each segent #ill also deterine a :designatedport; #hich sends the best BPDU on the segent$


13/80

Spanning-Tree BP"s

• .ll s#itches using STP ust e%change Bridge ProtocolData Units #ith other s#itches$

• Sent e'er) 2 seconds on e'er) acti'e port$


14/80

BP"s

The e%change of BPDU essages results in the follo#ing*

+The election of a root s#itch

+The election of a designated s#itch for e'er)

s#itched segent

+The reo'al of loops in the s#itched net#ork b)placing redundant s#itch ports in a backup state


15/80

BP"s

Bridge protocol data unit

%B()*&


16/80

"etailed *ields of BP"


17/80

Bridge I"

The Bridge !) contained in the B()* is used to determine the oot

Bridge


18/80

Bridge I"

• Consists of t#o coponents*7$ . 28b)te priorit)* Cisco s#itch defaults to 5 or

6%5666$

2$ . >8b)te M.C address

• Used to elect a root bridge$

• 1o#est Bridge ,D is the root$ + 1o#est Priorit) or M.C address

• ,f all de'ices ha'e the sae priorit)& the bridge #iththe lo#est M.C address becoes the root bridge$


19/80

/0tended Syste, I"

• Cisco runs a proprietar) Spanning Tree Protocolcalled Per ?1.3 Spanning Tree !P?ST"$

• Because !P?ST" re0uires that a separate instanceof spanning tree run for each ?1.3& the bridge ,D

field is re0uired to carr) ?1.3 ,D !?,D" inforation$ +To fit the ?,D info$ ,nto the original 7> B)tes of a B,D aportion of the priorit) field is used as the E%tended S)ste,D to carr) a ?,D$ +Because of the liited bit count& priorit) is no# con'e)edin discreet 'alues in increents of @6A> rather than

discreet 'alues in increents of 7 as the) #ould be #iththe full 7>8bit field a'ailable$


20/80

/0tended Syste, I" in t$e BI"


21/80

%oot Bridge /lection


22/80

%oot Port

• oot Port* The port recei'ing the best BPDU on abridge is the root port$

+ This is the port that is the closest to the root bridge

in ters of path cost

+ The root bridge sends BPDUs that are ore useful

than the ones that an) other bridge can send$

+ The root bridge is the onl) bridge in the net#ork

that does not ha'e a root port$


23/80

"esignated Port

• . port is designated if it can send the best BPDU on thesegent to #hich it is connected$

• n a gi'en segent& there can be onl) one path to#ard theroot bridge other#ise redundant paths #ould create abridging loop$

+ .ll bridges connected to a gi'en segent listen to eachothers BPDUs and agree on the bridge sending thebest BPDU as the designated bridge for the segent$


24/80

Spanning-Tree Lin! 1osts

Shortest path is based on cumulative lin' costs.

#in' costs are based on the speed of the lin'.


25/80

Spanning-Tree Topology /0a,ple


26/80

Spanning-Tree Port States

These values have been calculated on an assumption that there

will be a ma+imum of seven switches %diameter of seven& in an"

branch of the spanning tree from the root bridge.


27/80

Spanning-Tree Port States

• The Ma% .ge allo#s topolog) change inforation topropagate fro one side of the net#ork to the other$

• ,n the listening state& s#itches deterine if there arean) other paths to the root bridge and path cost is

copared$• ,n the learning state user data is not for#arded& but

M.C addresses are learned fro an) traffic that isseen$

• ,n the for#arding state user data is for#arded andM.C addresses continue to be learned$


28/80

STP Topology 1$ange

Topolog" Change otification B()*s are propagated toward the ootThe root bridge then changes the -lag portion of outbound B()*s

to indicate that a topolog" change is occurring.

hen switches receive the topolog" change configuration message

f rom the root bridge, the" use the forward dela" timer to age out entriesin the MAC address table.http/00www.cisco.com0en0*S0tech0t'30t'4210technologies5tech5note6314a666637838.shtm l

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080094797.shtmlhttp://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080094797.shtmlhttp://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080094797.shtml


29/80

Bac!&p %oot Bridge

A bac'up %or secondar"& root bridge is a switch that is preferentiall"

configured to assume the role of the root bridge in the event that

the primar" root bridge fails.

ith (9ST:, Bac'up oot bridges can als

load balance on a 9#A b" 9#A basis.


30/80

1onfig&ring a Pri,ary and Secondary

%oot


31/80

1o,,on Spanning Tree and PST

• The 562$7D standard for spanning tree assues that asingle instance of spanning tree runs for all ?1.3s$

+This is kno#n as Coon Spanning Tree !CST"

• Per ?1.3 Spanning Tree !P?ST" pro'ides the option topotentiall) establish a root bridge on a ?1.3 b) ?1.3basis$


32/80

1ST and PST


33/80

Spanning Tree Port*ast

• Spanning Tree PortFast causes an interfaceconfigured as a 1a)er 2 access port to transitionfro blocking to for#arding state iediatel)&

b)passing the listening and learning states$


34/80

Port*ast 1onfig&ration

Switch%config&;interface range fa601 $

Switch%config$if$range&;spanning$tree portfast


35/80

erifying Port*ast 1onfig&ration


36/80

Spanning-Tree BP" 3&ard and *iltering

• Cisco pro'ides t#o features to protect SpanningTree fro loops being created on ports #herePortFast has been enabled$

+BPDUs are not e%pected on portfast interfaces !ports"

• BPDU guard and BPDU filtering pro'ide protectionin case BPDUs are recei'ed on a PortFast interface$

+Both can be configured globall) or on a port8b)8port basis


37/80

BP" 3&ard and BP" *iltering


38/80

BP" 3&ard

• BPDU Guard is used to protect the s#itched net#ork fro theprobles that a) be caused b) the receipt of BPDUs on ports#hich should not be recei'ing the$

+These ports #ould be PortFast ports !edge ports"

+This a) be accidental or a) be an attept to add an

unauthoried s#itch to the net#ork +BPDU Guard #ill shutdo#n ports !err8disable"

• BPDU Guard can be configured either globall) or on a per portbasis$

Switch(config)# spanning-tree portfast bpduguard default

Switch(config-if)# spanning-tree bpduguard enable


39/80

BP" *iltering

• PortFast BPDU filtering effects ho# the s#itch ackno#ledges BPDUsseen on PortFast8configured ports$

• (hen BPDU Filtering is enabled& the s#itch #ill not send or recei'eBPDUs out of PortFast enabled s#itchports$

+BPDU Filtering does not shutdo#n the port like BPDU Guard does

• BPDU Filtering can be configured either globall) or on a per port basis$Switch(config)# spanning-tree portfast bpdufilter defaultSwitch(config-if)# spanning-tree bpdufilter enable

• ,n global configuration& if a BPDU is recei'ed on a Port Fast8enabledport& the port loses its Port Fast8operational status& and BPDU filtering isdisabled$

• ,n interface configuration& BPDU Filtering turns off Spanning Treebecause BPDUs are no longer sent or recei'ed$


40/80

BP" 3&ard 1onfig

BP" *il 1 fi


41/80

BP" *ilter 1onfig

BP" % t 3 d


42/80

BP" %oot 3&ard

• oot guard liits the s#itch ports out of #hich the rootbridge a) be negotiated$

• ,f a root guard8enabled port recei'es BPDUs that aresuperior to those being sent b) the current root bridge&then that port #ill be o'ed to a root8inconsistent state#hich is e0ual to an STP listening state$

% t 3 d 1 fi


43/80

%oot 3&ard 1onfig

guard

root

li !* t


44/80

plin!*ast

• Spanning Tree UplinkFast pro'ides fast con'ergence after adirect link failure !#ithin seconds"$

• This iediate con'ergence is facilitated through the creationof an uplink group + .n uplink group is a set of 1a)er 2 interfaces on a single

s#itch& onl) one of #hich is for#arding at an) gi'en tie$ + .n uplink group consists of the root port !#hich is for#arding"

and a set of blocked ports$ + ,f a port in the uplink group goes do#n& the s#itch #ill flood

the M.C address of its C.M table out of the ne# uplink$

• UplinkFast is ipleented on an access s#itch #ith at leastone for#arding port and one blocked port to#ard the root$

li !* t


45/80

plin!*ast

I di t Li ! * il


46/80

Indirect Lin! *ail&re

B !b * t


47/80

Bac!bone*ast

• BackboneFast addresses the situation #here an indirect failurecauses a topolog) change and a s#itch ust find an alternati'epath through an interediate s#itch$

+ BackboneFast is initiated #hen a root port or blocked port on as#itch recei'es inferior BPDUs fro its designated bridge$

• B) using the BackboneFast feature& the net#ork reco'ers fro anindirect failure in t#o ties the for#ard dela) tie !


48/80

Bac!bone*ast /0a,ple

B !b * t 1 fi


49/80

Bac!bone*ast 1onfig

/t$er1$annel


50/80

/t$er1$annel

• EtherChannel bundles indi'idual Ethernet links into a single logical linkthat pro'ides band#idth up to 7>66 Mbps !Fast EtherChannel fullduple%" or 7> Gbps !Gigabit EtherChannel" bet#een t#o Catal)sts#itches$

+ .ll interfaces in each EtherChannel ust be the sae speed and duple%and ust all be configured as either 1a)er 2 or 1a)er < interfaces$

+,f a link #ithin the EtherChannel bundle fails& traffic pre'iousl) carried o'erthe failed link #ill be carried o'er the reaining links #ithin theEtherChannel

• Each EtherChannel has a logical port channel interface$ + . configuration applied to the port channel interface affects all ph)sicalinterfaces assigned to that interface$

/t$er1$annel /0a,ple


51/80

/t$er1$annel /0a,ple

>therchannel -eatures and Benefits/?Allows for the creation of a ver"$high$bandwidth logical lin'

?#oad balances amongst the ph"sical lin's involved

?(rovides automatic failover

?Simplifies subse@uent logical configuration

?%configuration is per logical lin' instead of per ph"sical lin'&

P4gP and L41P


52/80

P4gP and L41P

• The Port .ggregation Protocol !P.gP" is a Ciscoproprietar) protocol that aids in the autoatic creationof Fast EtherChannel links$

• 1ink .ggregation Control Protocol !1.CP" is part of an,EEE specification !562$


53/80

/t$er1$annel +odes

This ode enables Etherchannel*• :n; 8 This is the ode that forces the interface to channel #ithout

P.gP or 1.CP$The ne%t t#o odes enable P.GP*

• :.uto; 8 This P.gP ode places an interface in a passi'e negotiatingstate in #hich the interface responds to the P.gP packets it recei'es&

but it does not initiate P.gP negotiation$• :Desirable; 8 This P.gP ode places an interface in an acti'enegotiating state in #hich the interface initiates negotiations #ith otherinterfaces b) sending P.gP packets$

+ ,nterfaces configured in the on ode do not e%change P.gP packets$ +The default ode for P.gP is auto ode$

/t$er1$annel +odes t$at &se L41P


54/80

/t$er1$annel +odes t$at &se L41P

• :Passi'e; 8 This 1.CP ode places a port into a passi'enegotiating state$

+,n this state& the port responds to the 1.CP packets

that it recei'es& but it does not initiate 1.CP packet

negotiation !default"$

• :.cti'e; 8 This 1.CP ode places a port into an acti'enegotiating state$

+,n this state& the port initiates negotiations #ith other

ports b) sending 1.CP packets$

/t$er1$annel 1onfig&ration


55/80

/t$er1$annel 1onfig&ration

/t$er1$annel Load Balancing


56/80

/t$er1$annel Load Balancing

• EtherChannel balances traffic load across the links in a channel$• To configure EtherChannel load balancing& use the coand* port-channel load-balancetype

• The load8balancing ke)#ords are as follo#s*src8ac 8 Source M.C addresses

dst8ac 8 Destination M.C addressessrc8dst8ac 8 Source and destination M.C addressessrc8ip 8 Source ,P addressesdst8ip 8 Destination ,P addressessrc8dst8ip 8 Source and destination ,P addresses !default"src8port 8 Source TCP4User Datagra Protocol !UDP" port

dst8port 8 Destination TCP4UDP portsrc8dst8port 8 Source and destination TCP4UDP port

3&idelines for 1onfig&ring /t$er1$annel


57/80

3&idelines for 1onfig&ring /t$er1$annel

ote for Instr&ctorsote for Instr&ctors


58/80

ote for Instr&ctorsote for Instr&ctors

• These presentations are the result of a collaboration aongThese presentations are the result of a collaboration aongthe instructors at St$ Clair College in (indsor& ntario$the instructors at St$ Clair College in (indsor& ntario$

• Thanks ust go out to ick Graiani of Cabrillo College$ HisThanks ust go out to ick Graiani of Cabrillo College$ Hisaterial and additional inforation #as used as a referenceaterial and additional inforation #as used as a reference

in their creation$in their creation$• ,f an)one finds an) errors or oissions& please let e kno#,f an)one finds an) errors or oissions& please let e kno#at*at*

+ tdaeIstclaircollege$ca$tdaeIstclaircollege$ca$

Spanning Tree Protocol (STP)Spanning Tree Protocol (STP)


59/80

Spanning Tree Protocol (STP)Spanning Tree Protocol (STP)

(9ST:, TS( and apid (9ST:(9ST:, TS( and apid (9ST:

Per8?1.3 Spanning TreePer8?1.3 Spanning Tree !P?ST"!P?ST"Per8?1.3 Spanning TreePer8?1.3 Spanning Tree !P?ST"!P?ST"

Multiple Spanning Tree ProtocolMultiple Spanning Tree Protocol !MSTP"!MSTP"Multiple Spanning Tree ProtocolMultiple Spanning Tree Protocol !MSTP"!MSTP"

apid Per8?1.3 Spanning Tree Plusapid Per8?1.3 Spanning Tree Plus !apid P?STJ"!apid P?STJ"apid Per8?1.3 Spanning Tree Plusapid Per8?1.3 Spanning Tree Plus !apid P?STJ"!apid P?STJ"

apid Spanning Treeapid Spanning Tree !STP"!STP"apid Spanning Treeapid Spanning Tree !STP"!STP"

Per8?1.3 Spanning Tree PlusPer8?1.3 Spanning Tree Plus !P?STJ"!P?STJ"Per8?1.3 Spanning Tree PlusPer8?1.3 Spanning Tree Plus !P?STJ"!P?STJ"

1isco and I/// STP ariants


60/80

1isco and I/// STP ariants

PST5 (1isco)


61/80

• Cisco P?STJCisco P?STJ** + A network can run an STP instance for A network can run an STP instance for each VLAN each VLAN in thein the

network.network.

• Cisco proprietar)$Cisco proprietar)$

• More than one trunkMore than one trunk can block for a ?1.3$can block for a ?1.3$

• 1oad sharing1oad sharing can be ipleented$can be ipleented$

• Means thatMeans that all s#itchesall s#itches in the net#ork are engaged inin the net#ork are engaged incon'ergingcon'erging the net#ork$the net#ork$

• S#itch ports ha'e to accoodate theS#itch ports ha'e to accoodate the additionaladditional

band#idthband#idth used for BPDUs$used for BPDUs$• DefaultDefault for Cisco 2A>6 s#itches$for Cisco 2A>6 s#itches$

PST5 (1isco)

PST5 (1isco)


62/80

PST5 (1isco)

E%tended S)ste8,DE%tended S)ste8,DE%tended S)ste8,DE%tended S)ste8,D

PST5 (1isco)


63/80

PST5 (1isco)

E%tended S)ste8,DE%tended S)ste8,DE%tended S)ste8,DE%tended S)ste8,D

1onfig&re PST5


64/80

1onfig&re PST5

%apid Spanning-Tree Protocol (%STP)


65/80

• ,EEE 562$7# STP*,EEE 562$7# STP*

+ What is it?What is it?• ,s an e'olution of the 562$7D standard$,s an e'olution of the 562$7D standard$

• Terinolog) reains priaril) the sae$Terinolog) reains priaril) the sae$

• Most paraeters ha'e been left unchanged$Most paraeters ha'e been left unchanged$

• Speeds the recalculation of the spanning tree on a topolog)Speeds the recalculation of the spanning tree on a topolog)change$change$

• Much faster con'ergence$Much faster con'ergence$

• edefines the t)pe of ports and their state$edefines the t)pe of ports and their state$

• .lternate or backup ports can iediatel) change to a for#arding .lternate or backup ports can iediatel) change to a for#arding

state #ithout #aiting for the net#ork to con'erge$state #ithout #aiting for the net#ork to con'erge$




66/80

• ,EEE 562$7# STP*,EEE 562$7# STP* + Characteristics:Characteristics:

• Preferred protocolPreferred protocol

for pre'entingfor pre'enting

1a)er 2 loops$1a)er 2 loops$

• Cisco8proprietar)Cisco8proprietar)

enhanceents& such as UplinkFast and BackboneFast&enhanceents& such as UplinkFast and BackboneFast&

are not copatible #ith STP$are not copatible #ith STP$

• etains back#ard copatibilit) to 562$7D$etains back#ard copatibilit) to 562$7D$

• Keeps the sae BPDU forat as ,EEE 562$7D #ith theKeeps the sae BPDU forat as ,EEE 562$7D #ith the

'ersion field is set to 2 to indicate STP$'ersion field is set to 2 to indicate STP$

• Port can safel) transition to the for#arding state #ithoutPort can safel) transition to the for#arding state #ithout

ha'ing to rel) on an) tier configuration$ha'ing to rel) on an) tier configuration$

%apid Spanning Tree Protocol (%STP)



67/80


562$7# !STP"562$7# !STP"

S#itch sends anS#itch sends an

inforation BPDU e'er)inforation BPDU e'er)hello tie !2 seconds"hello tie !2 seconds"

e'en if no BPDU hase'en if no BPDU has

been recei'ed on thebeen recei'ed on the

root port$root port$

562$7# !STP"562$7# !STP"

S#itch sends anS#itch sends an

inforation BPDU e'er)inforation BPDU e'er)hello tie !2 seconds"hello tie !2 seconds"

e'en if no BPDU hase'en if no BPDU has

been recei'ed on thebeen recei'ed on the


562$7D !STP"562$7D !STP"

S#itchS#itch onl)onl) sends ansends an

inforation BPDU #heninforation BPDU #henit recei'es one on theit recei'es one on the


562$7D !STP"562$7D !STP"

S#itchS#itch onl)onl) sends ansends an

inforation BPDU #heninforation BPDU #henit recei'es one on theit recei'es one on the




68/80

• apid Transition to For#arding State*

+ Rapi transition is the !ost i!portant feature introuce "# $%&.'w.

• The legac) ST. passi'el) #aited for the net#ork to con'erge

before it turned a port into the for#arding state$

• The ne# rapid STP is able to acti'el) confir that a port can safel)

transition to the for#arding state #ithout ha'ing to rel) on an)

tier configuration$

• ,n order to achie'e fast con'ergence on a port& the protocol relies

upon t#o ne# 'ariables*

+ Edge Ports

+ 1ink T)pe$




69/80

• Edge Ports*Edge Ports*

+ .n edge port is a s#itch port that is ne'er intended to be connected to .n edge port is a s#itch port that is ne'er intended to be connected toanother s#itch de'ice$another s#itch de'ice$

+ ,t iediatel) transitions to the for#arding state #hen enabled$,t iediatel) transitions to the for#arding state #hen enabled$

+ (oes this soun like an#thing we(oes this soun like an#thing we)*e alrea# iscusse?)*e alrea# iscusse?


• 3on8Edge Ports3on8Edge Ports**

• A non$edge port is a switch port that is alwa"s intended to be connected toanother switch device.

Cisco 8 PortfastCisco 8 PortfastCisco 8 PortfastCisco 8 Portfast

3on8Edge Ports3on8Edge Ports3on8Edge Ports3on8Edge Ports

Edge PortsEdge PortsEdge PortsEdge Ports



70/80

• 1ink T)pes1ink T)pes** + The link t)pe pro'ides a categoriation for each portThe link t)pe pro'ides a categoriation for each port

participating in STP$participating in STP$

+ 3on8edge3on8edge ports are categoried intoports are categoried into t#o link t)pest#o link t)pes**

• Point8to8point*Point8to8point*

+ Connects to a single net#ork de'ice$Connects to a single net#ork de'ice$

• Shared*Shared*

+ Connects to a shared edia #here ore s#itchesConnects to a shared edia #here ore s#itches

a) e%ist$a) e%ist$ + The link t)pe isThe link t)pe is autoaticall)autoaticall) deri'ed fro thederi'ed fro the duple%duple%

ode of a portode of a port but this can be o'erridden$but this can be o'erridden$




71/80

• 1ink T)pes1ink T)pes**

+ +owe*er, "efore the link t#pe para!eter is consiere, RSTP !ust+owe*er, "efore the link t#pe para!eter is consiere, RSTP !usteter!ine the port role.eter!ine the port role.

• oot Ports*oot Ports*

+ Do notDo not use the link t)pe paraeter$use the link t)pe paraeter$

• .lternate and Backup Ports* .lternate and Backup Ports*

+ Do notDo not use the link t)pe paraeter in ost cases$use the link t)pe paraeter in ost cases$

• Designated Ports*Designated Ports*

+ Make the ost use of the link t)pe paraeter onl) if it is aMake the ost use of the link t)pe paraeter onl) if it is a

point8to8point link$point8to8point link$




72/80

• Port StatesPort States** + .n STP topolog) change causes a transition to the .n STP topolog) change causes a transition to the

for#arding state through eitherfor#arding state through either e%plicit handshakese%plicit handshakes or aor a

proposal and agreeent process and s)nchroniationproposal and agreeent process and s)nchroniation$$

• (ith STP& the(ith STP& the rolerole of a port isof a port is separatedseparated fro thefro the

statestate of a port$of a port$

+ For e%aple& a designated port could be in theFor e%aple& a designated port could be in the

discarding state teporaril)& e'en though its finaldiscarding state teporaril)& e'en though its final

state is to be for#arding$state is to be for#arding$




73/80

• Port StatesPort States** + Discarding*Discarding*

• Pre'ents the for#arding of data fraes$Pre'ents the for#arding of data fraes$

+ 1earning*1earning*

• .ccepts data fraes to populate the M.C table$ .ccepts data fraes to populate the M.C table$ + For#arding*For#arding*

• For#ards data fraes and deterines the topolog)$For#ards data fraes and deterines the topolog)$




74/80


STPSTPSTPSTP

STPSTPSTPSTP



75/80

• Port olesPort oles** + The port role defines the ultiate purpose of a s#itch portThe port role defines the ultiate purpose of a s#itch port

and ho# it handles data fraes$ Port roles and port statesand ho# it handles data fraes$ Port roles and port states

are able to transition independentl) of each other$are able to transition independentl) of each other$

• ootoot PortPort

• DesignatedDesignated PortPort

• .lternate .lternate PortPort

• BackupBackup PortPort

+ Creating the additional port roles allo#s STP to define aCreating the additional port roles allo#s STP to define astandb) s#itch portstandb) s#itch port before a failurebefore a failure or topolog) change$or topolog) change$

p p g ( )



76/80

• Port olesPort oles**

p p g ( )

%STP Proposal and 4gree,ent Process


77/80

• ,n ,EEE 562$7D STP*,n ,EEE 562$7D STP* + . . designated port ust #aitdesignated port ust #ait t#o ties the for#ard dela)t#o ties the for#ard dela)

before transitioning the port to the for#arding state$before transitioning the port to the for#arding state$

• STP*STP* + Significantl) speeds up the recalculation process after aSignificantl) speeds up the recalculation process after a

topolog) change$topolog) change$ + ,t,t con'erges on a link8b)8link basiscon'erges on a link8b)8link basis andand does not rel) ondoes not rel) on

tierstiers e%piring before ports can transition$e%piring before ports can transition$

+ nl) onnl) on edge portsedge ports andand point8to8pointpoint8to8point links$links$

p g

%STP Proposal and 4gree,ent Process


78/80

p g

1onfig&ring %apid-PST5


79/80

• apid P?STJ is a Cisco ipleentation of STPapid P?STJ is a Cisco ipleentation of STP$$ + Supports spanning tree forSupports spanning tree for each ?1.3each ?1.3$$

+ apid STP 'ariantapid STP 'ariant to use in Cisco8based net#orks$to use in Cisco8based net#orks$

g g p

"esign STP for Tro&ble 4voidance


80/80

• Final Points*Final Points*

g

Documents

CCNP3v4_Mod03 SPT Day 1.4 Ver 2