H3C S5120V3-EI Series Troubleshooting Manual page 30

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To display the global QoS policy configuration, execute the display qos policy global
command.
b. Verify that packets are not filtered out by automatically created ACLs.
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The IP source guard feature creates ACLs automatically.
Execute the display this command in Ethernet interface view to verify that the ip
source guard command is configured on the port. To display source guard binding
entries, execute the display ip source binding or display ipv6 source binding
command. If the ip source binding command or ip verify source command is
configured but the packets match no entry, further troubleshoot the issue based on the
way the binding entries are created.
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The EAD assistant feature creates ACLs automatically.
The EAD assistant feature discards packets for a user that fails authentication when the
user accesses an IP address not in the free IP segment.
Execute the display dot1x command to verify that the EAD assistant feature is enabled.
If the EAD assistant feature is enabled, identify whether the user fails the authentication
and accesses an IP address not in the free IP segment.
3. Verify that the port is not blocked:
Execute the display stp brief command to verify that STP does not set the state of the port
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to discarding. When the port is in discarding state, it cannot forward traffic. H3C
recommends that you disable STP on the port, or configure the port as an edge port if the
port is connected to a terminal device.
If the port belongs to an aggregation group, execute the display link-aggregation verbose

command to identify the port status. When the port is an Unselected port, it cannot forward
traffic. Locate the reasons why the port is in Unselected state. For example, the attribute
configurations of the port are different from the configurations of the reference port.
If the port belongs to a smart link group, execute the display smart-link group command to

verify the port status. The port cannot forward packets if its state is standby or down. If the
port is standby, configure the port as a primary port. If the port is down, verify the causes and
resolve the issue as required. A port might go down if the uplink device is configured with the
monitor link function, the port is shut down, or the link fails.
4. Examine the following configurations that might cause packet loss:
VLAN configuration—Execute the display this command in Ethernet interface view to
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verify that the port is in the VLAN of the packets. If it is not, add the port to the VLAN.
Blackhole MAC address entries—Execute the display mac-address blackhole
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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 interface command.
If congestion occurs, locate and resolve the issue by referencing related congestion
management documents.
6. If the issue persists, contact H3C Support.
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