7705 SAR Interfaces
112
Interface Configuration Guide
3HE 11011 AAAC TQZZA Edition: 01
3.2.13.5 Hold-down Timers
Hold-down timers control how quickly a LAG responds to operational port state
changes. The following timers are supported:
• port-level hold-time (up/down) timer
This timer controls the delay before a port is added to or removed from a LAG
when the port comes up or goes down. Each port in the LAG has the same timer
value, which is configured on the primary LAG link (port). The timer is set with
the config>port>ethernet>hold-time command.
• subgroup-level hold-down timer
This timer controls the delay before a switch from the current subgroup to a new
candidate subgroup, selected by the LAG subgroup selection algorithm. The
timer is set with the config>lag>selection-criteria command.
The timer can be configured to never expire, which prevents a switch from an
operationally up subgroup to a new candidate subgroup. This setting can be
manually overridden by using the tools>perform>force>lag-id command (refer
to the 7705 SAR OAM and Diagnostics Guide, “Tools Command Reference”, for
information on this command).
If the port-level timer is set, it must expire before the subgroup selection occurs
and this timer is started. The subgroup-level timer is supported only for LAGs
running LACP.
• LAG-level hold-down timer
This timer controls the delay before a LAG is declared operationally down when
the available links fall below the required port or bandwidth minimum. This timer
is recommended for MC-LAG operation. The timer prevents a LAG from being
brought down when an MC-LAG switchover executes a make-before-break
switch. The LAG-level timer is set with the config>lag>hold-time down
command.
If the port-level timer is set, it must expire before the LAG operational status is
processed and this timer is started.
3.2.13.6 Multi-Chassis LAG
Multi-chassis LAG (MC-LAG) is a redundancy feature on the 7705 SAR, useful for
nodes that are taken out of service for maintenance, upgrades, or relocation.
MC-LAG also provides redundancy for incidents of peer nodal failure. Refer to the
“Multi-Chassis LAG Redundancy” section in the 7705 SAR Basic System
Configuration Guide.
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