Virtual Link Aggregation Control Protocol - Avaya 8600 Configuration Manual

Virtual Link Aggregation Control Protocol

Virtual Link Aggregation Control Protocol (VLACP) is an extension to LACP used for end-to-
end failure detection. VLACP is not a link aggregation protocol. It is a mechanism to periodically
check the end-to-end health of a point-to-point connection. VLACP uses the Hello mechanism
of LACP to periodically send Hello packets to ensure an end-to-end communication. When
Hello packets are not received, VLACP transitions to a failure state, which indicates a service
provider failure and that the port is disabled.
The VLACP only works for port-to-port communications where there is a guarantee for a logical
port-to-port match through the service provider. VLACP does not work for port-to-multiport
communications where there is no guarantee for a point-to-point match through the service
provider. You can configure VLACP on a port.
VLACP can also be used with MLT to complement its capabilities and provide quick failure
detection. VLACP is recommended for all SMLT access links when the links are configured as
MLT to ensure both end devices are able to communicate. By using VLACP over Single-Port
SMLT, enhanced failure detection is extended beyond the limits of the number of SMLT or
LACP instances that can be created on an Avaya switch.
VLACP trap messages are sent to the management stations if the VLACP state changes. If
the failure is local, the only traps that are generated are port linkdown or port linkup.
The Ethernet cannot detect end-to-end failures. Functions such as remote fault indication or
far-end fault indication extend the Ethernet to detect remove link failures. A major limitation of
these functions is that they terminate at the next Ethernet hop. They cannot determine failures
on an end-to-end basis.
For example, in
networks connect the aggregated Ethernet trunk groups through a service provider network
connection (for example, through a VPN), far-end failures cannot be signaled with Ethernet-
based functions that operate end-to-end through the service provider network. The MultiLink
trunk (between Enterprise switches S1 and S2) extends through the Service Provider (SP)
network.
Figure 10: Problem description (1 of 2)
can operate end-to-end, but can be used in a point-to-point link.
Configuration — Link Aggregation, MLT, and SMLT
Figure 10: Problem description (1 of 2)
Virtual Link Aggregation Control Protocol
on page 44 when the Enterprise
on page 44 shows a MLT running with VLACP. VLACP
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