Chapter 20: Ip Configuration: Sla; Overview - Cisco 350 Series Administration Manual

IP Configuration: SLA
NOTE

Overview

Cisco 350, 350X and 550X Series Managed Switches, Firmware Release 2.4, ver 0.4
This feature is only supported in the 550 family of switches.
This chapter describes how the Service Level Agreement (SLA) feature works.
It covers the following topics:
• Overview
• Using SLA
IP SLA Tracking for VRRP
VRRP specifies an election protocol that dynamically assigns responsibility for a virtual router
to one of the routers in the network. The router with the highest VRRP priority is selected as
the network master router, and all other routers are backup routers. Upon master router failure
the backup router with the highest VRRP priority becomes the master router.
The VRRP protocol provides information on the state of the router itself, but does not provide
information about the states of the routes used by the router. Therefore, when using static
routing, a situation may exist where the master router continues to act as master router, since it
is functional, although connectivity from the router to the (default route) next hop is lost. IP
VRRP SLA provides a mechanism to track the connectivity to the VRRP router default route
next hop. If connectivity to the next hop is lost, the master router VRRP priority is
decremented, thus allowing backup routers with higher priority (than the decremented value)
to take over and become the master router. This enables connectivity to the next hop via the
new selected master router. IP SLA is not required when using RIP or other dynamic routing
protocols
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