H3C S5850-54QS, Troubleshooting Manual, Page: 49 / 54

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If the state of the port is DOWN , locate the reason for the port to be down. The possible
reasons include: its uplink device is configured with monitor link, the link of the port fails,
or the port is shut down. Further troubleshoot the issue based on the reason for the port
to be down.
−
If the state of the port is STANDBY , perform an active/standby switchover in the smart
link group.
4. Examine the following configurations that might cause packet loss:

VLAN configuration —Execute the
display this
command in Ethernet interface view to
verify that the VLAN of the packets is permitted by the port. If the VLAN is not permitted by
the port, modify the VLAN settings to enable the port to permit the VLAN.

Blackhole MAC address entries —Execute the
display mac-address blackhole
command to display blackhole MAC address entries. If the packets are discarded because
they match a blackhole MAC address entry, delete the entry. To delete the blackhole MAC
address entry, execute the
undo mac-address blackhole mac-address vlan
vlan-id
command.

Rate limit —Execute the
display qos lr interface
command to display the rate limit
configuration on the port. If rate limit is configured on the port, make sure the committed
information rate (CIR) and the committed burst size (CBS) are appropriate. To adjust the
CIR and CBS values, execute the
qos lr
{
inbound
|
outbound
}
cir
committed-information-rate
[
cbs committed-burst-size
] command.

Storm suppression —Execute the
display this
command in Ethernet interface view to
display the configuration of storm suppression. Storm suppression includes broadcast
suppression, multicast suppression, and unknown unicast suppression. To adjust the
suppression thresholds, execute the
broadcast-suppression
,
multicast-suppression
, and
unicast-suppression
commands, respectively.
5. Verify that no congestion occurs by using the
display qos queue-statistics
interface
command.
If congestion occurs, locate and resolve the issue by referencing related congestion
management documents.
6. If the issue persists, contact H3C Support.
Related commands
This section lists the commands that you might use for troubleshooting Layer 2 packet loss failure.
Command Description
display dot1x Displays information about 802.1X.
display interface Displays Ethernet interface information.
display ip source binding/display ipv6
source binding
Displays source guard binding entries.
display link-aggregation verbose
Displays detailed information about the
aggregation groups that correspond to the
aggregate interfaces.
display mac-address blackhole Displays blackhole MAC address entries.
display packet-filter
Displays whether an ACL has been successfully
applied to an interface for packet filtering.
display portal interface
Displays portal configuration and portal running
state on an interface.
display qos lr interface
Displays the rate limit configuration and statistics
on a specified interface or all the interfaces.