Avaya 8600 Configuration Manual page 42

Link aggregation fundamentals
users should note that if VLACP is admin disabled on one side of the link/connection, this
will cause VLACP to bring the associated remote connection down, but since the remote
connection will keep link up, the side with VLACP admin disabled, will now have a black-
hole connection to the remote switch, which will cause a drop of all packets being sent to it.
If VLACP is disabled on one side of a connection, it MUST also be disabled on remote side
or else traffic loss will likely occur. The same applies to LACP configurations for 1 port
MLTs.
Note:
LACP short timers for RSMLT/SMLT configurations must be set to 550 milliseconds or
higher.
Note:
If using VRRP with SMLT, users MUST use unique VRIDs, especially when scaling VRRP
(more than 40 instances). Use of a single VRID for all instances is supported within the
standard, but when such a configuration is used in scaled SMLT designs, instability could
be seen. An alternative method, which allows scaling to maximum number of IP VLANs, is
to use RSMLT designs instead.
Note:
For any SMLT design, for either RSMLT L2 Edge VLANs or L2 SMLT VLANs using VRRP,
it is now HIGHLY recommended to change the default VLAN FDB aging timer from its default
value of 300 seconds, to now be 1 second higher that the system setting for the ARP aging
timer. FDB timers are set on a per VLAN basis. If using the default system ARP aging time,
config ip arp aging <minutes>, of 360 (minutes) than the proper value for the FDB aging
timer, config vlan x fdb-entry aging-time <seconds>, should be 21601 seconds, which is 360
minutes (6 hours) plus 1 second. This will have the system only use the ARP aging timer
for aging, versus the FDB aging timer. This value has been shown to work very well to assure
no improper SMLT learning. The use of this timer has one potential side-affect: this limits
the system to around a maximum of 64,000 concurrent MACs, even with timer setting. With
this timer, should an edge device move, the system will still immediately re-learn and re-
populate the FDB table properly, and not have to wait for the 6 hour (plus 1 second) timer
to expire. No negative operational affects are known when using this timer value. For non-
SMLT based VLANs the default FDB aging timer of 300 maybe used or can be changed or
even also set to 21601. For this reason the default value of the FDB aging timer will remain
at 300 (seconds), within all code releases.
Note:
There are now new and improved informational and warning log messages associated with
SMLT. Some messages will be generated for normal SMLT failovers, but additionally these
messages can assist with troubleshooting any abnormal SMLT activity. Under abnormal
conditions, please contact Avaya Technical Support for further assistance, and provide the
exact log messages generated.
42 Configuration — Link Aggregation, MLT, and SMLT
Comments? infodev@avaya.com
January 2012