Figure 6: Designated, Root, And Alternate Ports - Juniper JUNOS OS 10.4 Manual

Copyright © 2012, Juniper Networks, Inc.
Configure MSTP on Router 3:
3.
[edit]
protocols {
mstp {
configuration-name mstp-for-R1-2-3; # The names must match to be in the same
region
revision-level 3; # The revision levels must match
interface ae2;
interface ae3;
msti 1 {
vlan100; # This VLAN corresponds to MSTP instance 1
}
msti 2 {
vlan200; # This VLAN corresponds to MSTP instance 2
bridge-priority 4096; # This bridge acts as VLAN 200 designated bridge on
# the R2-R3 segment
}
}
}
As a result of this configuration, VLAN 100 and VLAN 200 share physical links, but have
different designated ports, root ports, and alternate ports on the three different routers.
The designated, root, and alternate ports for the two VLANs on the three routers are
shown in Figure 6 on page

Figure 6: Designated, Root, and Alternate Ports

Chapter 2: Basic Layer 2 Features on MX Series Routers
33.
33