Multilink Trunking - Avaya 8800 Planning And Engineering

Redundant network design

MultiLink Trunking

MultiLink trunking is used to provide link layer redundancy. You can use MultiLink Trunking
(MLT) to provide alternate paths around failed links. When you configure MLT links, consider
the following information:
• Software Release 7.0 supports 128 MLT aggregation groups with up to 8 ports (R or RS
series modules and R mode required).
• Up to eight same-type ports can belong to a single MLT group. The same port type means
that the ports operate on the same physical media, at the same speed, and in the same
duplex mode.
• For Release 7.0, MLT ports can run between an 8648GTR and other module types. MLT
ports must run at the same speed with the same interface type, even if using different I/
O module types.
MLT navigation
• MLT/LACP groups and port speed
• Switch-to-switch MLT link recommendations
• Brouter ports and MLT
• MLT and spanning tree protocols
• MLT protection against split VLANs
MLT/LACP groups and port speed
Ensure that all ports that belong to the same MLT/LACP group use the same port speed, for
example, 1 Gbit/s, even if autonegotiation is used. The software does not enforce this
requirement. Avaya recommends that you use CANA to ensure proper speed negotiation in
mixed-port type scenarios.
To maintain LAG stability during failover, use CANA: configure the advertised speed to be the
same for all LACP links. For 10/100/1000 ports, ensure that CANA uses one particular setting,
for example, 1000-full or 100-full. Otherwise, a remote device can restart autonegotiation and
the link can use a different capability.
It is important that each port uses only one speed and duplex mode. This way, all links in Up
state are guaranteed to have the same capabilities. If autonegotiation and CANA are not used,
the same speed and duplex mode settings must be used on all ports of the MLT.
Switch-to-switch MLT link recommendations
Avaya recommends that physical connections in switch-to-switch MLT and link aggregation
links be connected in a specific order. To connect an MLT link between two switches, connect
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November 2010