Juniper Networks 10.4 ExampleStep: Configuring Spanning Tree Protocols

ExampleStep: Configuring Spanning Tree Protocols
Configurethe Spanning TreeProtocol on all three routers. This is necessary toavoid the
potentialbridging loop formed by the triangular architectureof the routers. MSTP is
configuredon the three routers so the set of VLANs has an independent, loop-free
topology.TheLayer 2 traffic can be load-shared over65 independent paths (64 Multiple
SpanningTreeInstances [MSTIs] and one Common and Internal Spanning Tree[CIST]),
eachspanning a set of VLANs. Theconfiguration names, revision level,and VLAN-to-MSTI
mappingmust match in orderto utilize the load-sharing capabilities of MSTP (otherwise,
eachrouter will be in a different region).
Toconfigure the SpanningTree Protocol on all three routers:
1. ConfigureMSTP on Router 1:
[edit]
protocols{
mstp{
configuration-namemstp-for-R1-2-3; # The names must matchto be in the same
region
revision-level3; # The revision levelsmust match
bridge-priority0; # This bridge acts as root bridge forVLAN 100 and 200
interfaceae1;
interfaceae2;
msti1 {
vlan100;# This VLAN corresponds to MSTP instance1
}
msti2 {
vlan200;# This VLAN corresponds to MSTP instance2
}
}
}
2. ConfigureMSTP on Router 2:
[edit]
protocols{
mstp{
configuration-namemstp-for-R1-2-3; # The names must matchto be in the same
region
revision-level3; # The revision levelsmust match
interfaceae1;
interfaceae3;
msti1 {
vlan100;# This VLAN corresponds to MSTP instance1
bridge-priority4096; # This bridge acts as VLAN 100 designatedbridge on
#the R2-R3 segment
}
msti2 {
vlan200;# This VLAN corresponds to MSTP instance2
}
}
}
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Junos10.4 MX Series Ethernet ServicesRouters Solutions Guide