HP 5820X Series User Manual

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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 vary with vendors, the configuration digests calculated using private keys is
different. The different vendors’ devices in the same MST region cannot communicate with each other.
Enabling the digest snooping feature on the port connecting the local device to a third-party device in the
same MST region can make the two devices communicate with each other.
Before enabling digest snooping, ensure that associated devices of different vendors are connected and
run MSTP.
Configuring the digest snooping feature
You can enable digest snooping only on a device that is connected to a third-party device that uses its
private key to calculate the configuration digest.
To configure digest snooping:
To do... Use the command... Remarks
1. Enter system view
system-view —
Enter Ethernet
interface view or
Layer 2 aggregate
interface view
interface interface-type interface-
number
2. Enter
interface
view or port
group view
Enter port group
view
port-group manual port-group-
name
Required.
Use either command.
3. Enable digest snooping on the
interface or port group
stp config-digest-snooping
Required.
Disabled by default.
4. Return to system view
quit —
5. Enable global digest snooping
stp config-digest-snooping
Required.
Disabled by default.
With the digest snooping feature enabled, comparison of configuration digest is not needed for in-the-
same-region check, so the VLAN-to-instance mappings must be the same on associated ports.
With global digest snooping enabled, modification of VLAN-to-instance mappings and removing of the
current region configuration using the undo stp region-configuration command are not allowed. You can
only modify the region name and revision level.
You must enable digest snooping both globally and on associated ports to make it take effect. HP
recommends that you enable digest snooping on all associated ports first and then globally, making the
configuration take effect on all configured ports and reducing impact on the network.
To avoid loops, do not enable digest snooping on MST region edge ports.
HP recommends that you enable digest snooping first and then MSTP. To avoid traffic interruption, do not
configure digest snooping when the network works well.
Digest snooping configuration example
1. Network requirements

HP 5820X Series Specifications

General

Brand	HP
Model	5820X Series
Category	Switch
Language	English