User`s guide

Overview of Spanning Tree Protocols
Matrix DFE Series and N-SA User’s Guide 5-5
•FormatSelector‐Oneoctetinlengthandisalways0.Itcannotbeadministrativelychanged.
• ConfigurationName‐Auser‐assigned,casesensitivenamegiventotheregion.The
maximumlengthofthenameis32octets.
• RevisionLevel‐Twooctetsinlength.Thedefaultvalueof0maybeadministrativelychanged.
• Configuration
Digest‐16octetHMAC‐MD5signaturecreatedfromtheconfiguredVLAN
Identification(VID)/FilteringIdentification(FID)toMultipleSpanningTreeInstances(MSTI)
mappings.Alldevicesmusthaveidenticalmappingstohaveidenticalconfigurationdigests.
TheMSTregiondesignatesoneCISTregionalrootbridgefortheregion,regardlessofthenumber
of
MSTIs.TheregionalrootprovidestheconnectivityfromtheregiontotheCISTroot,whenthe
CISTrootliesoutsidetheregion.
Multiple Spanning Tree Instances (MSTI)
InsidetheMSTregion,aseparatetopologyismaintainedfromtheoutsideworld.EachMST
regionmaycontainupto64differentMSTIs.TheMatrixDFESeriesorN‐SAdevicemapsVLAN
IDs(VIDs)andFilteringIDs(FIDs)toeachotherinaonetoonecorrelation;forexample,FID
3=
VID3.VID/FIDsaremappedtodifferentMSTIstocreateatypeofloadbala ncing.
Determining FID-to-SID Mappings
VLANsaremappedtoMSTIsthroughaFID‐to‐SIDmappingcorrelationwhichisthekeyelement
inMSTPconfiguration.EachVLANisassociatedtoaFIDand,duringMSTIcreation,VLANsare
mappedtospanningtreeIDsusingtheirFIDassociation.Thismappingiscontainedwithinthe
MSTconfigurationdigest
describedintheprevioussection anddisplayedinthefollowing
example.Bydefault,everybridgewillhaveaFID‐to‐SIDmappingthatequalsVLANFID1/SID0.
UsethiscommandtodetermineMSTIconfigurationidentifierinformation,andwhetherornot
thereisamisconfigurationduetonon‐matchingconf igurationidentifier
components:
show spantree mstcfigid
Example
ThisexampleshowshowtodisplayMSTIconfigurationidentifierinformation.Inthiscase,
thisbridgebelongsto“Region1”:
InorderforotherbridgestobelongtoRegion1,allfourelementsofthosebridges’configuration
IDoutputmustmatch.Theonlydefaultvaluethatmustbechangedforthistohappenis
the
configurationnamesetting,asfollows
:
UsethiscommandtochangetheconfigurationnamefromthedefaultbridgeMACaddressvalue
to“Region1”:
set spantree mstcfgid cfgname Region1
SinceanMSTIisaseparatespanningtree,eachMSTIhasitsownrootinsidetheMSTregion.
Figure 5‐2andFigu re 5‐3showtwoMSTIsinasingleregion.Device3istherootforMSTI1,
Device2istherootforMSTI2,andDevice5isthe
CISTregionalroot.TrafficforalltheVLANs
attachedtoanMSTIfollowtheMSTI’sspannedtopology.
Matrix->show spantree mstcfgid
MST Configuration Identifier:
Format Selector: 0
Configuration Name: Region1
Revision Level: 88
Configuration Digest: 6d:d7:93:10:91:c9:69:ff:48:f2:ef:bf:cd:8b:cc:de