Avaya 8800 Planning And Engineering, Network Design page 58

Redundant network design
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 SLT, 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 Figure 13: Problem description (1 of 2)
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 13: Problem description (1 of 2)
operate end-to-end, but can be used in a point-to-point link.
Figure 13: Problem description (1 of 2)
In the following figure, if the L2 link on S1 (S1/L2) fails, the link-down failure is not propagated over
the SP network to S2 and S2 continues to send traffic over the failed S2/ L2 link.
June 2016
on page 58 when the Enterprise networks
on page 58 shows a MLT running with VLACP. VLACP can
Planning and Engineering — Network Design
Comments on this document? infodev@avaya.com
58