Exam 2V0-21.19 topic 1 question 92 discussion

In the ACTUAL version of the exam, in the question, the word "PREVENT" is changed to "DETECT". Accordingly, the correct answer is D: Beacon Probin

B is correct. The Question is: „Which Network Failure Detection Policy will PREVENT network failover?“

The answer is correct.

Beacon Probing is the correct answer. Link State detects direct connection between vmnic and physical switch. Beacon Probing detects failures behind the connected physical switches

correct answer => D. Beacon probing

Beacon probing Sends out and listens for Ethernet broadcast frames, or beacon probes, that physical NICs send to detect link failure in all physical NICs in a team. ESXi hosts send beacon packets every second. Beacon probing is most useful to detect failures in the closest physical switch to the ESXi host, where the failure does not cause a link-down event for the host. Use beacon probing with three or more NICs in a team because ESXi can detect failures of a single adapter. If only two NICs are assigned and one of them loses connectivity, the switch cannot determine which NIC needs to be taken out of service because both do not receive beacons and as a result all packets sent to both uplinks. Using at least three NICs in such a team allows for n-2 failures where n is the number of NICs in the team before reaching an ambiguous situation. https://docs.vmware.com/en/VMware-vSphere/6.5/com.vmware.vsphere.networking.doc/GUID-4D97C749-1FFD-403D-B2AE-0CD0F1C70E2B.html

Its clearle Beacon probing, the image describes the scenario, the clue to solve is about Link status does not detect disconnection behind the switch connecter to the vNIC, it relays just in link status connection via cable or if the switch is power on. But according with this: "Pulled cable that connects a physical switch to another networking devices, for example, an upstream switch". There is no manner to Link Status can detect that connection failure. By the other hand, it says: "Beacon probing is most useful to detect failures in the closest physical switch to the ESXi host", It means it may detect using "Ethernet broadcast frames, or beacon probes" some kind of failure on switcher closest to host, about the image Links status only willl NOT detect that failure because will always have LINK UP because switch is power on and BEACON can detect events has been not causes by LINK-DOWN..

Link Status and Beacon probing are not policies. Also, Link Status detects network failure from bad adapters or cable pulls. If you look at the diagram, the break is beyond Switch 1 so the first link is still operational, just not transmitting traffic. You need to use "Notify Switches" so the tables can be updated of the failure.

VMware are ambiguous. What should the following mean?!!!: Link status only detects failures, such as removed cables and physical switch power failures. However, link status does not detect the following configuration errors: Pulled cable that connects a physical switch to another networking devices, for example, an upstream switch . https://docs.vmware.com/en/VMware-vSphere/7.0/com.vmware.vsphere.networking.doc/GUID-4D97C749-1FFD-403D-B2AE-0CD0F1C70E2B.html

How does beacon probing work? Beacon probing is a network failover detection mechanism that sends and listens for beacon probe packets on all physical NICs in the team. In a teamed uplink packets will be sent through each physical NIC.

the correct answer is D

For Beacon Probing, nics might be in active/standby mode. So, there may be failover. Link Status only Relies only on the link status that the network adapter provides. This option detects failures such as removed cables and physical switch power failures. Beacon Probing Sends out and listens for beacon probes on all NICs in the team, and uses this information, in addition to link status, to determine link failure.ESXi sends beacon packets every second. The NICs must be in an active/active or active/standby configuration because the NICs in an unused state do not participate in beacon probing.

Correct answer D. Checked in egzam.

D - is the correct answer

Correct answer: D Monitoring the link status provided by the network adapter detects failures like cable pulls and physical switch power failures. This monitoring does not detect configuration errors, such as a physical switch port being blocked by the Spanning Tree Protocol or misconfigured VLAN membership. This method cannot detect upstream, nondirectly connected physical switch or cable failures. Beaconing introduces a 62-byte packet load approximately every 1 second per physical NIC. When beaconing is activated, the VMkernel sends out and listens for probe packets on all NICs that are configured as part of the team. This technique can detect failures that link-status monitoring alone cannot. Consult your switch manufacturer to verify the support of beaconing in your environment. See the VMware Knowledge Base article 1005577 at http://kb.vmware.com/kb/1005577.

Link status will probably detect the NIC link are all up since the direct attached ports are all functioning. To go further upstream, you need beacon probing to relay the port status correctly as the uplink switch is now broken. Hence likely answer is beacon probing https://blogs.vmware.com/vsphere/2008/12/using-beaconing-to-detect-link-failures-or-beaconing-demystified.html

B is the answer. According to this doc. https://docs.vmware.com/en/VMware-vSphere/6.0/com.vmware.vsphere.networking.doc/GUID-4D97C749-1FFD-403D-B2AE-0CD0F1C70E2B.html There is a description about "link status only" : Pulled cable that connects a physical switch to another networking devices, for example, an upstream switch . This description is totally meet the question environment.