Design Reference

VLACP. VLACP takes the point-to-point hello mechanism of LACP and uses it to periodically send
PDU packets to ensure end-to-end reachability and provide failure detection, across a Layer 2
domain. If one end of the link does not receive the VLACP PDUs, it logically disables that port and
no traffic passes. This action ensures that even if no link exists on the port at the other end, and if it
is not processing VLACP PDUs correctly, no traffic is sent. This function alleviates potential black
hole situations by sending traffic only to ports that are functioning properly.
You can reduce VLACP timers to 400 milliseconds between two VSP 4000 systems. The timer
provides approximately 1-second failure detection and switchover. When you configure VLACP, you
must configure both ends of the link with the same multicast MAC address and timers. Most
products in the Avaya Ethernet Switch and Ethernet Routing Switch line use the same timers, with
the exception of the FastPeriodicTimer, which is 200 milliseconds on the Ethernet Routing Switch
8800, VSP 9000, and VSP 4000; and 500 milliseconds on all other switches.
SLPP example scenarios
The following examples illustrate some situations where Layer 2 loops can occur and how SLPP
prevents loops in those cases.
Scenario 1: VSP 4000 as an edge router
Scenario 1 demonstrates a triangular setup with ERS 8800 switches as vIST peers, and VSP 4000
on the edge. From VSP 4000, there are four links that are part of the same MLT, with SLPP enabled
on the VSP 4000 ports. Because the MLT ports are misconfigured, loops can occur. For example,
port 1/1 on VSP 4000 can be part of the MLT, but on the ERS port, 2/1 is not part of the MLT,
although they are on the same VLAN.
SLPP example scenarios
June 2015 Network Design Reference for Avaya VSP 4000 Series 45
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