Design Reference

LACP and spanning tree interaction
Only the physical link state or the LACP peer status affects the operation of LACP. When a link
changes state between UP and DOWN, the LACP module receives notification. The spanning tree
forwarding state does not affect the operation of the LACP module. LACP data units (LACPDU) can
be sent even if the port is in spanning tree blocking state.
Configuration changes (such as speed and duplex mode) made to a LAG member port do not apply
to all the member ports of the MLT. Instead, the changed port is removed from the LAG, and the
corresponding aggregator and user is alerted.
In contrast to MLT, IEEE 802.3ad-based link aggregation does not require the system to replicate
BPDUs over all ports in the trunk group.
LACP and minimum link
The minimum link function defines the minimum number of active links required for a LAG to remain
in the forwarding state. You cannot configure the minimum link on VSP 4000. The minimum link
value is always 1.
If the number of active links in a LAG is 0, the entire LAG is declared down and VSP 4000 informs
the remote end of the LAG state by using an LACPDU.
Link aggregation group rules
Link aggregation is compatible with RSTP and MSTP. LAGs operate using the following rules:
• All ports in a LAG must operate in full-duplex mode.
• All ports in a LAG must use the same data rate.
• All ports in a LAG must be in the same VLANs.
• LAGs form using LACP.
• The platform supports a maximum of 128 LAGs.
• Each LAG supports a maximum of eight active links.
For LACP fundamentals and configuration procedures, see Avaya Virtual Services Platform 4000
Series Configuration — Link Aggregation and MLT, NN46251-503.
Link redundancy
44 Network Design Reference for Avaya VSP 4000 Series January 2015
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