352-001 · Question #785
Company A has a hub-and spoke topology over an SP-managed infrastructure. To measure traffic performance metrics. IP SLA senders on all spoke CE routers and an IP SLA responder on the hub CE router…
The correct answer is D. CPU usage on the hub router. In a hub-and-spoke IP SLA deployment with a single hub responder and many spoke senders, the hub CPU is the critical resource to monitor because it must process probe responses from every spoke simultaneously as the site count grows.
Question
Company A has a hub-and spoke topology over an SP-managed infrastructure. To measure traffic performance metrics. IP SLA senders on all spoke CE routers and an IP SLA responder on the hub CE router. What must they monitor to have visibility on the potential performance impact due to the constantly increasing number of spoke sites?
Options
- Amemory usage on the hub router
- Binterface buffers on the hub and spoke routers
- CCPU and memory usage on the spoke routers
- DCPU usage on the hub router
How the community answered
(33 responses)- A15% (5)
- B3% (1)
- C9% (3)
- D73% (24)
Why each option
In a hub-and-spoke IP SLA deployment with a single hub responder and many spoke senders, the hub CPU is the critical resource to monitor because it must process probe responses from every spoke simultaneously as the site count grows.
IP SLA responder session state consumes minimal memory per session; memory is not the primary resource that scales proportionally with the number of spoke sites.
Interface buffer utilization reflects traffic volume and congestion, not the number of IP SLA sessions, so it does not directly indicate the scaling impact of additional spoke sites.
Each spoke router only originates its own single IP SLA session and is unaffected by how many other spoke sites exist, so spoke CPU and memory do not scale with topology growth.
The hub CE router is the sole IP SLA responder for all spoke routers, so its CPU load scales linearly with the number of spokes - each new spoke adds concurrent probe processing overhead to the hub, making CPU utilization the primary indicator of performance degradation risk.
Concept tested: IP SLA hub responder CPU scalability
Source: https://www.cisco.com/c/en/us/support/docs/ip/ip-service-level-agreements-ip-sla/116349-technote-ipsla-00.html
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