300-540 Exam Dumps : Designing and Implementing Cisco Service Provider Cloud Network Infrastructure (SPCNI v1.0)

Comprehensive and Detailed Explanation (Cisco NFVI / Virtualization Knowledge)

SR-IOV (Single Root I/O Virtualization)allows a VM to access the network interface hardwaredirectly, without going through the hypervisor’s virtual switch.

This is achieved by:

Assigning Virtual Functions (VFs) directly to VMs

Allowing high-performance, low-latency packet I/O

Bypassing the hypervisor datapath

Therefore, SR-IOV doesnotbypass the guest OS; it bypasses thehypervisor I/O virtualization layer, delivering near-native performance.

Thus the correct answer isC.

In Cisco data center and cloud-scale designs, adouble-sided vPC(also called vPC-to-vPC) is used when both ends of a Layer 2 port channel are formed by a pair of switches that operate as vPC peers. In this model:

On the aggregation or leaf side, two switches (in this case,LEAF1 and LEAF2) form a vPC domain with a vPC peer-link and keepalive.

On the access or ToR side, two switches (in this case,TOR1 and TOR2) must also form their ownvPC domainwith a peer-link and vPC keepalive.

The port-channel that interconnects the two vPC domains is then configured as a vPC on both sides, creating a vPC-to-vPC topology.

The problem statement specifies thatLEAF1 and LEAF2 are already configured as vPC peers. For a double-sided vPC to work, the other side (TOR1 and TOR2) must also behave as a single logical entity for the downstream Cisco UCS server and for the upstream vPC connection towards LEAF1 and LEAF2. This is only achieved when TOR1 and TOR2 are configured as vPC peers with:

A vPC domain ID

A vPC peer-link between TOR1 and TOR2

vPC member port-channels towards LEAF1 and LEAF2 and towards the Cisco UCS server

Therefore, the next required step is to configure avPC between TOR1 and TOR2.

Evaluation of the options:

Option A, “Add all the switches to the fabric,” is generic and not specific to vPC configuration. It does not address the technical requirement to form a vPC domain on the ToR side.

Option B, “Configure peering between LEAF1 and LEAF2 and TOR1 and TOR2,” is incorrect because vPC peering is only configured between the two switches that form each vPC domain (LEAF1–LEAF2 and TOR1–TOR2), not across all four switches together.

Option C, “Configure MSTP between TOR1 and TOR2,” is not required for establishing a double-sided vPC. vPC designs rely on the vPC control plane and the peer-link, not on spanning-tree between the vPC peers for normal operation.

Option D, “Configure a vPC between TOR1 and TOR2,” correctly describes configuring TOR1 and TOR2 as a vPC pair (vPC domain with peer-link), which is the mandatory step to create a double-sided vPC topology with LEAF1 and LEAF2.

InCisco Enterprise NFVIS, time synchronization is configured using thesystem time ntpcommand structure. NFVIS requires a primary and optionally a backup NTP server to maintain accurate system time for the hypervisor and guest VMs.

Correct NFVIS command syntax for NTP configuration:

system time ntp preferred_server This command configures thepreferred (primary)NTP server used for system clock synchronization.

system time ntp backup_server This command configures thebackupNTP server, which the system uses if the primary becomes unreachable.

These two commands match Cisco NFVIS time-configuration behavior described in NFV infrastructure design and implementation guidelines.

Why the Correct Answers Are A and E

Option A: system time ntp preferred_server 192.168.1.1

This properly configures the primary NTP server in NFVIS. The preferred server is always the first choice for time synchronization.

Option E: system time ntp backup_server 192.168.2.1

This correctly configures the backup NTP server. If the preferred server fails, NFVIS automatically falls back to the backup server.

Both commands directly match NFVIS’s NTP command hierarchy and are the only ones that correctly apply to NFVIS.

Why the Other Options Are Not Correct

Option Buses utils ntp, which is not an NFVIS command.

Option Csets manual time and does not configure NTP servers.

Option Dalso uses the utils ntp syntax, which applies to other Cisco platforms but not NFVIS.