Juniper EX9200 Features Manual page 100

Spanning-Tree Protocols Feature Guide for EX9200 Switches
Table 11: Components of the Topology for Configuring MSTP on EX Series Switches (continued)
Property
Switch 3
Switch 4
VLAN names and tag IDs
MSTIs
MSTI region
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Settings
The following interfaces on Switch 3 are connected in this way:
is connected to Switch 1
ge-0/0/26
is connected to Switch 2
ge-0/0/28
ge-0/0/24 is connected to Switch 4
The following interfaces on Switch 4 are connected in this way:
is connected to Switch 1
ge-0/0/19
is connected to Switch 3
ge-0/0/23
, tag
voice-vlan 10
, tag
employee-vlan 20
, tag
guest-vlan 30
, tag
camera-vlan 40
1
2
region1
The topology in Figure 2 on page 83
The CIST is a single spanning tree connecting all devices in the network. The switch with
the lowest bridge priority is elected as the root bridge of the CIST. You can control the
election of the root bridge by configuring the bridge priority. Switch 3 is the root bridge
of the CIST.
The ports in an MSTP topology have specific roles:
The root port is responsible for forwarding data to the root bridge.
The alternate port is a standby port for the root port. When a root port goes down, the
alternate port becomes the active root port.
The designated port forwards data to the downstream network segment or device.
The backup port becomes the active designated port and starts forwarding data when
the designated port goes down.
In this example, one MSTP region contains Switch 1, Switch 2, Switch 3, and Switch 4.
Within the region, four VLANs are created:
supports voice traffic and has the VLAN tag identifier of
voice-vlan
supports data traffic and has the VLAN tag identifier of
employee-vlan
supports guest VLAN traffic (for supplicants that fail authentication) and
guest-vlan
has the VLAN tag identifier of
camera-vlan supports video traffic and has the VLAN tag identifier of
shows a common and internal spanning tree (CIST).
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30
Copyright © 2017, Juniper Networks, Inc.
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10
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20
40 .