3com 5500-ei pwr Installation Instruction
1-39
As a result, STP calculation is performed repeatedly, which may occupy too much CPU of the switches
or cause errors in the protocol state of the BPDU packets.
or cause errors in the protocol state of the BPDU packets.
In order to avoid this problem, you can enable BPDU dropping on Ethernet ports. Once the function is
enabled on a port, the port will not receive or forward any BPDU packets. In this way, the switch is
protected against the BPDU packet attacks so that the STP calculation is assured to be right.
enabled on a port, the port will not receive or forward any BPDU packets. In this way, the switch is
protected against the BPDU packet attacks so that the STP calculation is assured to be right.
Configuration Prerequisites
MSTP runs normally on the switch.
Configuration procedure
Follow these steps to configure BPDU dropping:
To do...
Use the command...
Remarks
Enter system view
system-view
—
Enter Ethernet port view
interface
interface-name
—
Enable BPDU dropping
bpdu-drop any
Required
BPDU dropping is disabled by default.
BPDU dropping is disabled by default.
Configuration example
# Enable BPDU dropping on Ethernet 1/0/1.
<Sysname>system-view
[Sysname] interface Ethernet 1/0/1
[Sysname-Ethernet1/0/1] bpdu-drop any
Configuring Digest Snooping
Introduction
According to IEEE 802.1s, two interconnected switches can communicate with each other through
MSTIs in an MST region only when the two switches have the same MST region-related configuration.
Interconnected MSTP-enabled switches determine whether or not they are in the same MST region by
checking the configuration IDs of the BPDUs between them (A configuration ID contains information
such as region ID and configuration digest).
MSTIs in an MST region only when the two switches have the same MST region-related configuration.
Interconnected MSTP-enabled switches determine whether or not they are in the same MST region by
checking the configuration IDs of the BPDUs between them (A configuration ID contains information
such as region ID and configuration digest).
As some other manufacturers' switches adopt proprietary spanning tree protocols, they cannot
communicate with the other switches in an MST region even if they are configured with the same MST
region-related settings as the other switches in the MST region.
communicate with the other switches in an MST region even if they are configured with the same MST
region-related settings as the other switches in the MST region.
This problem can be overcome by implementing the digest snooping feature. If a port on a 3Com switch
5500-EI is connected to another manufacturer's switch that has the same MST region-related
configuration as its own but adopts a proprietary spanning tree protocol, you can enable digest
snooping on the port. Then the switch 5500-EI regards another manufacturer's switch as in the same
region; it records the configuration digests carried in the BPDUs received from another manufacturer's
switch, and put them in the BPDUs to be sent to the another manufacturer's switch. In this way, the
switch 5500-EI can communicate with another manufacturer’s switches in the same MST region.
5500-EI is connected to another manufacturer's switch that has the same MST region-related
configuration as its own but adopts a proprietary spanning tree protocol, you can enable digest
snooping on the port. Then the switch 5500-EI regards another manufacturer's switch as in the same
region; it records the configuration digests carried in the BPDUs received from another manufacturer's
switch, and put them in the BPDUs to be sent to the another manufacturer's switch. In this way, the
switch 5500-EI can communicate with another manufacturer’s switches in the same MST region.