Which two statements are true about unified ISSU? (Choose two.)
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A. B. C. D.BD
Unified In-Service Software Upgrade (ISSU) is a feature that enables network devices to upgrade their software without disrupting traffic or causing downtime. It allows the network to run with different versions of software during the upgrade process, making the upgrade process non-disruptive.
The two statements that are true about unified ISSU are:
A. It allows gradual implementation of new features.
Unified ISSU allows gradual implementation of new features by enabling the upgrade of software on individual network devices without causing a network-wide disruption. This means that new features can be rolled out gradually, without disrupting the network's existing services.
B. It reduces operating costs while delivering higher service levels.
Unified ISSU reduces operating costs by enabling network devices to be upgraded without taking them out of service. This means that maintenance windows can be reduced or eliminated altogether, resulting in higher service levels and increased network availability.
C. It involves network down time during software image upgrades.
This statement is false. Unified ISSU allows network devices to be upgraded without causing downtime or disruption to network services. This means that users can continue to access the network while software upgrades are taking place.
D. It requires graceful Routing Engine switchover (GRES) and nonstop active routing (NSR).
This statement is true. Unified ISSU requires GRES and NSR to ensure that network devices can switch to new software versions without disrupting network services. GRES enables the device to switch to a standby Routing Engine, while NSR ensures that the device can continue to forward packets during the switch. Together, GRES and NSR ensure that software upgrades can be performed without causing network downtime or service disruption.