Operation Manual – MSTP
H3C S3610&S5510 Series Ethernet Switches
Chapter 1 MSTP Configuration
1-41
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Ethernet 1/1 on Switch A and Ethernet 1/2 on Switch B allow the traffic of VLAN 1
to pass through. Ethernet 1/3 on Switch A and Ethernet 1/4 on Switch B allow the
traffic of VLAN 2 to pass through.
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Switch A is the root bridge, and both Switch A and Switch B run MSTP. Ethernet
1/4 on Switch B is blocked, causing traffic block on VLAN 2.
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Configure VLAN Ignore to make the blocked port forward packets.
II. Network diagram
Figure 1-7
VLAN Ignore configuration
III. Configuration procedure
1)
Enable VLAN Ignore on Switch B
# Enable VLAN Ignore on VLAN 2.
<SwitchB> system-view
[SwitchB] stp ignored vlan 2
2)
Verify the configuration
# Display the VLAN Ignore enabled VLAN.
[SwitchB] display stp ignored-vlan
STP-Ignored VLAN: 2
1.7 Configuring Digest Snooping
As defined in IEEE 802.1s, interconnected devices are in the same region only when
the region-related configuration (domain name, revision level, VLAN-to-instance
mappings) on them is identical. An MSTP enabled device identifies devices in the same
MST region via checking the configuration ID in BPDU packets. The configuration ID
includes the region name, revision level, configuration digest that is in 16-byte length
and is the result calculated via the HMAC-MD5 algorithm based on VLAN-to-instance
mappings.
Since MSTP implementations differ with vendors, the configuration digest calculated
using private key is different; hence different vendors’ devices in the same MST region
can not communicate with each other.
Enabling the Digest Snooping feature on the associated port can make a device
communicate with another vendor’s device in the same MST region.