Configuring Digest Snooping - HP A5830 Configuration Manual

Figure 18 VLAN Ignore configuration
Root
bridge
GE1/0/1
GE1/0/2
Device A
Root port
Normal link
Configuration procedure
2.
# Enable VLAN Ignore for VLAN 2 on Device B.
<DeviceB> system-view
[DeviceB] stp ignored vlan 2
# Display the VLAN Ignore-enabled VLAN.
[DeviceB] display stp ignored-vlan
STP-Ignored VLAN: 2

Configuring Digest Snooping

CAUTION:

To take effect, Digest Snooping must be enabled both globally and on associated ports. To reduce network
impact while making the configuration effective on all configured ports:
a. First enable Digest Snooping on all associated ports first
b. Then enable it globally.

To prevent loops, do not enable Digest Snooping on MST region edge ports.

HP recommends enabling Digest Snooping before enabling the spanning tree feature. To avoid causing traffic
interruption, do not configure Digest Snooping when the network is already working well.
As defined in IEEE 802.1s, connected devices are in the same region only when their MST region-related
configurations (region name, revision level, and VLAN-to-instance mappings) are identical. A spanning
tree device identifies devices in the same MST region by determining the configuration ID in BPDU
packets. The configuration ID includes the region name, revision level, and configuration digest, which is
in 16-byte length and is the result calculated via the HMAC-MD5 algorithm based on VLAN-to-instance
mappings.
Spanning tree implementations vary with vendors, and the configuration digests calculated using private
keys is different, so devices of different vendors in the same MST region cannot communicate with each
other.
Enabling Digest Snooping
To enable communication between an HP device and a third-party device, enable the Digest Snooping
feature on the port that connects the HP device to the third-party device in the same MST region.
Before you enable Digest Snooping, make sure that associated devices of different vendors are connected
and run spanning tree protocols.
Enable Digest Snooping only on the HP device that is connected to a third-party device that uses its
private key to calculate the configuration digest.
VLAN 1
GE1/0/1
GE1/0/2
VLAN 2
Device B
Designated port Blocked port
Blocked link
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