Design Reference

MLT and spanning tree protocols
The implementation of 802.1w (Rapid Spanning Tree Protocol—RSTP) and 802.1s (Multiple
Spanning Tree Protocol—MSTP), provides a path cost calculation method. The following table
provides the path costs associated with each interface type:
Table 10: Path cost for RSTP or MSTP mode
Link speed Recommended path cost
Less than or equal 100 Kb/s 200 000 000
1 Mb/s 20 000 000
10 Mb/s 2 000 000
100 Mb/s 200 000
1 Gb/s 20 000
10 Gb/s 2000
100 Gb/s 200
1 Tb/s 20
10 Tb/s 2
802.3ad-based link aggregation
Link aggregation provides link layer redundancy. Use IEEE 802.3ad-based link aggregation
(IEEE 802.3 2002 clause 43) to aggregate one or more links together to form LAGs to allow a
MAC client to treat the LAG as if it were a single link. Use link aggregation to increase aggregate
throughput of the interconnection between devices and provide link redundancy. LACP can
dynamically add or remove LAG ports, depending on their availability and states.
Although IEEE 802.3ad-based link aggregation and MLT provide similar services, MLT is
statically defined. By contrast, IEEE 802.3ad-based link aggregation is dynamic and provides
additional functionality.
LACP and MLT
When you configure standards-based link aggregation, you must enable the aggregatable
parameter. This configuration creates a one-to-one mapping between the LACP aggregator
and the specified MLT.
A newly-created MLT or LAG adopts the VLAN membership of its member ports after the first
port attaches to the aggregator associated with this LAG. After a port detaches from an
aggregator, the port is deleted from the associated LAG port member list. After the last port
member is deleted from the LAG, the LAG is deleted from all VLANs.
After you configure the MLT as aggregatable, you cannot add or delete ports or VLANs
manually.
Link redundancy
40 Network Design Reference for Avaya VSP 4000 February 2014
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