Multiple Stp - ZyXEL Communications GS3700 Series User Manual

I n t he following exam ple, t here are t wo RSTP inst ances ( M RSTP1 and M RSTP2 ) on swit ch A.
Figure 86 MRSTP Net work Exam ple
To set up MRSTP , act ivat e MRSTP on t he Swit ch and specify which port ( s) belong t o which spanning
t ree.
Not e: Each port can belong t o one STP t ree only.

11.1.5 Multiple STP

Mult iple Spanning Tree Prot ocol ( I EEE 802.1s) is backwards com pat ible wit h STP/ RSTP and
addresses t he lim it at ions of exist ing spanning t ree prot ocols ( STP and RSTP) in net works t o include
t he following feat ures:
• One Com m on and I nt ernal Spanning Tree ( CI ST) t hat represent s t he ent ire net work's
connect ivit y.
• Grouping of m ult iple bridges ( or swit ching devices) int o regions t hat appear as one single bridge
on t he net work.
• A VLAN can be m apped t o a specific Mult iple Spanni n g Tree I nst ance ( MSTI ) . MSTI allows
m ult iple VLANs t o use t he sam e spanning t ree.
• Load- balancing is possible as t raffic from differe nt VLANs can use dist inct pat hs in a region.
11.1.5.1 MSTP Network Example
The following figure shows a net work exam ple where t wo VLANs are configured on t he t wo
swit ches. I f t he swit ches are using STP or RSTP , t he link for VLAN 2 will be blocked as STP and RSTP
allow only one link in t he net work and block t he redundant link.
Chapter 11 Spanning Tree Protocol
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