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System Settings
Configuring ASR 5500 Link Aggregation ▀
ASR 5500 System Administration Guide, StarOS Release 17 ▄
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Multiple Switches with L2 Redundancy
To handle the implementation of LACP without requiring standby ports to pass LACP packets, two separate instances
of LACP are started on redundant cards. The two LACP instances and port link state are monitored to determine
whether to initiate an auto-switch (including automatic L2 port switch).
of LACP are started on redundant cards. The two LACP instances and port link state are monitored to determine
whether to initiate an auto-switch (including automatic L2 port switch).
The figure below shows an LAG established across two MIO/UMIO daughter card ports with L2 redundancy.
Figure 8.
LAG with L2 Redundancy, Two Ethernet Switches
An LACP implementation with L2 redundancy cannot pass traffic even though standby ports have link up. For example,
with two MIO/UMIO cards connected to two different Ethernet switches and all ports in the same LAG, failure of ports
would not trigger a LAG switch until the active port number ratio flipped (more ports down than up).
with two MIO/UMIO cards connected to two different Ethernet switches and all ports in the same LAG, failure of ports
would not trigger a LAG switch until the active port number ratio flipped (more ports down than up).
Port States for Auto-Switch
Ports are classified in one of four states to determine whether to start auto-switching. See the table below.
For counters, State(x) represents the number of ports on a card in that state.
Table 5. Auto-Switch Port States
State
Counter
Description
Link
L(x)
Physical link up
Standby
S(x)
Link up but in standby mode
Waiting
W(x)
Waiting for Link Aggregation Control Protocol negotiation
Aggregated
A(x)
Aggregation formed
Hold Time
Once the LAG manager switches to another LACP instance, it does not consider another change for a short period to let
link and LACP negotiation settle down. This “hold time” is configurable.
link and LACP negotiation settle down. This “hold time” is configurable.
The LAG manager also enters/extends the hold period when an administrator manually switches ports to trigger a card
switch.
switch.