400-007 · Question #229
The controller has a global view of the network, and it can easily ensure that the network is in a consistent and optimal configuration. Which two statements describe a centralized SDN control path? (
The correct answer is C. A centralized controller can support all southbound APIs, which allows for easy integration with E. Scaling of the centralized controller cluster is challenging for services like DHCP and load-. Centralized SDN controllers offer broad southbound API support for device integration but face inherent scaling challenges for stateful services like DHCP and load balancing.
Question
The controller has a global view of the network, and it can easily ensure that the network is in a consistent and optimal configuration. Which two statements describe a centralized SDN control path? (Choose two.)
Options
- AIt significantly improves the latency when performing reactive handling of PACKET_IN events
- BIntegrating smart NIC capabilities on the local host level is made easier through rest APIs
- CA centralized controller can support all southbound APIs, which allows for easy integration with
- DIt is highly-available by design with no single-point-of-failure risks present
- EScaling of the centralized controller cluster is challenging for services like DHCP and load-
How the community answered
(21 responses)- A19% (4)
- B5% (1)
- C71% (15)
- D5% (1)
Why each option
Centralized SDN controllers offer broad southbound API support for device integration but face inherent scaling challenges for stateful services like DHCP and load balancing.
Centralized control increases latency for reactive PACKET_IN events because each packet must traverse the network to the remote controller and back before forwarding decisions are made, rather than being handled locally on the device.
Smart NIC integration at the local host level is characteristic of distributed or host-based SDN models, not centralized SDN architectures that manage forwarding decisions at the network device layer.
A centralized controller consolidates southbound API support, enabling communication with diverse network devices through protocols like OpenFlow, NETCONF, and RESTCONF, which simplifies integration across heterogeneous environments from a single control point.
A centralized controller is inherently a single point of failure; while clustering can partially mitigate this, it requires deliberate additional engineering and is not a built-in guarantee of the centralized model.
Scaling a centralized controller cluster is inherently difficult for stateful services such as DHCP and load balancing because these require consistent state synchronization across all controller instances, creating significant overhead as the cluster grows.
Concept tested: Centralized SDN controller benefits and scaling limitations
Source: https://www.cisco.com/c/en/us/solutions/software-defined-networking/overview.html
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