Users Guide

Optimizing Trac Disruption Over LAG Interfaces On
IOA Switches in VLT Mode
When you use the write memory command while an Aggregator operates in VLT mode, the VLT LAG congurations are saved in
nonvolatile storage (NVS).
By restoring the settings saved in NVS, the VLT ports come up quicker on the primary VLT node and trac disruption is reduced. The delay
in restoring the VLT LAG parameters is reduced (90 seconds by default) on the secondary VLT peer node before it becomes operational.
This makes sure that the conguration settings of the primary VLT node are synchronized with the secondary VLT peer node before the
secondary VLT mode is up. The trac outage is less than 200 millisconds during the restart or switchover of the VLT peer nodes from
primary to secondary.
Preserving LAG and Port Channel Settings in
Nonvolatile Storage
Use the write memory command on an I/O Aggregator, which operates in either standalone or PMUX modes, to save the LAG port
channel conguration parameters. This behavior enables the port channels to be brought up because the congured interface attributes are
available in the system database during the booting of the device. With the reduction in time for the port channels to become active after
the switch is booted, the loss in the number of packets that are serviced by these interfaces is minimized.
Enabling the LACP link fallback member
By default, the lacp link-fallback member-independent port-channel 128 command is enabled on the Standalone
mode. This command is not available in the VLT mode. To disable the
LACP link fallback member, use the no lacp link-
fallback member-independent port-channel 128 command.
The following log message appears when LACP link fallback is enabled:
Feb 26 15:53:32: %STKUNIT0-M:CP IFMGR-5-NO_LACP_PDU_RECEIVED_FROM_PEER: Connectivity to PEER is
restricted because LACP PDU's are not received. Verify the LACP configurations on PEER to bring
up the Uplink LAG to attain better bandwidth
The following log message appears when LACP link fallback is removed:
Feb 26 15:53:32: %STKUNIT0-M:CP %SMUX-5-SMUX_LACP_PDU_RECEIVED_FROM_PEER: LACP PDU received
from PEER and connectivity to PEER will be restored to Uplink Port-channel 128.
Enabling the Verication of Member Links Utilization
in a LAG Bundle
To examine the working eciency of the LAG bundle interfaces, perform the following steps:
1 The functionality to detect the working eciency of the LAG bundle interfaces is automatically activated on all the port channels,
except the port channel that is congured as a VLT interconnect link, during the booting of the switch.
2 Use the show link-bundle-distribution port-channel interface-number command to display the trac handling
and utilization of the member interfaces of the port channel. The following sample output is displayed when you enter this
show
command.
EXEC
Dell#show link-bundle-distribution port-channel
Dell#show link-bundle-distribution port-channel 1
Link-bundle trigger threshold - 60
LAG bundle - 1 Utilization[In Percent] - 0 Alarm State - Inactive
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Link Aggregation