CCNP ENCOR reference
IP SLA Quick Reference
Active reachability/performance testing and tracked objects — tested in ENCOR objective 4.5.
What IP SLA actually does
IP SLA generates synthetic test traffic (ICMP echo, UDP jitter, TCP connect, and more) on a schedule, measuring real reachability and performance — not just inferring health from routing protocol state, which can look fine even when actual end-to-end reachability has failed.
The operation → track → action chain
An IP SLA operation must be explicitly scheduled ('ip sla schedule ... start-time now') — a fully defined operation with no schedule never actually runs.
A tracked object ('track <id> ip sla <op> reachability') watches an operation's result — this is what other features (EEM, HSRP interface tracking, PBR) actually react to, not the raw IP SLA operation directly.
Reacting to the tracked object rather than the operation directly is a deliberate layer of indirection: the same tracked object can be reused by multiple consumers (an EEM applet AND an HSRP priority decrement, for example) without duplicating the underlying reachability test.
Verification
'show ip sla configuration' confirms an operation is actually scheduled, not just defined.
'show track <id>' shows the tracked object's current state (Up/Down) — if this doesn't reflect real-world reachability, check the IP SLA operation's own schedule and target before assuming the tracking/reaction logic itself is broken.