Avaya 8600 Configuration Manual page 52

Link aggregation fundamentals
after a dynamic configuration change, enter the following CLI command: conf mlt
<mlt-id> lacp clear-link-aggrgate
• When you configure SMLT links, Avaya recommends that you set the multicast packets-
per-second value to 6000 pps.
• Avaya recommends that you do not enable LACP on interswitch trunks to avoid
unnecessary processing. Use VLACP when an optical network between the SMLT core
switches requires a failure detection mechanism.
• Enabling mcast-mlt distribution on a square-mesh SMLT can cause loss of streams going
through the diagonal links. This results in traffic not being distributed properly. Avaya
recommends that you disable the diagonal links.
Using the SMLT system ID enables you to use any third-party switch as a wiring closet switch
in an SMLT configuration. This enhancement provides an option for the administrator to
configure the SMLT Core Aggregation Switches to always use the system ID. In this way, the
SMLT Core Aggregation Switch will always use the same LACP key regardless of the state of
SMLT Core Aggregation Switch neighbor (or the IST link). Therefore no change in LAGs should
occur on the attached device. This is the case regardless of whether the device is a server or
a third-party switch. This situation does not affect Avaya edge switches used in SMLT
configurations. The actor system priority of LACP_DEFAULT_SYS_PRIO, the actor system ID
the user configures, and an actor key equal to the SMLT-ID or SLT-ID are sent to the wiring
closet switch. Avaya recommends that you configure the system ID to be the base MAC
address of one of the aggregate switches along with its SMLT-id. The administrator must
ensure that the same value for system ID is configured on both of the SMLT Core Aggregation
Switches
The Avaya Ethernet Routing Switch 8800/8600 software does not support Simple Loop
Prevention Protocol (SLPP) in an LACP–SMLT environment.
With Release 4.1.8.2 and higher, an administrator can configure the LACP SMLT System ID
used by SMLT core aggregation switches. When you set the LACP system ID for SMLT,
configure the same LACP SMLT system ID on both aggregation switches to avoid the loss of
data.
An explanation of the importance of configuring the System ID is as follows. The LACP System
ID is the base MAC address of the switch, which is carried in Link Aggregation Control Protocol
Data Units (LACPDU). When two links interconnect two switches that run LACP, each switch
knows that both links connect to the same remote device because the LACPDUs originate
from the same System ID. If the links are enabled for aggregation using the same key, then
LACP can dynamically aggregate them into a LAG (MLT).
When SMLT is used between the two switches, they act as one logical switch. Both aggregation
switches must use the same LACP System ID over the SMLT links so that the edge switch
sees one logical LACP peer, and can aggregate uplinks towards the SMLT aggregation
switches. This process automatically occurs over the IST connection, where the base MAC
address of one of the SMLT aggregation switches is chosen and used by both SMLT
aggregation switches.
However, if the switch that owns that Base MAC address reboots, the IST goes down, and the
other switch reverts to using its own Base MAC address as the LACP System ID. This action
52 Configuration — Link Aggregation, MLT, and SMLT
Comments? infodev@avaya.com
January 2012