3V0-25.25 Practice Questions

The administrator should click thevmnic0interface on theESX-1 Host.

In aVMware Cloud Foundation (VCF)environment, theGENEVE (Generic Network Virtualization Encapsulation)protocol is the industry-standard tunnel format used by NSX to create an overlay network. This protocol allows Layer 2 traffic from virtual machines to be "tunneled" over a Layer 3 physical IP fabric, enabling workloads to communicate as if they were on the same segment even when separated by physical routers.

When VM-1 on ESX-1 sends an ICMP request to VM-2 on ESX-2, the packet starts as a standard Ethernet frame at the virtual machine'svnic1. At this stage, the packet contains no encapsulation. As the frame enters theVirtual Distributed Switch (VDS)and hits theTunnel End Point (TEP), the host's kernel performs the encapsulation process. The TEP adds a GENEVE header, a UDP header (port 6081), and an outer IP header.

Thevmnic0(physical NIC) on the source host (ESX-1) is the specific "egress" point where this transformation is complete. A packet capture taken at this physical interface will show the "Outer IP" address of the source TEP and destination TEP, with the original ICMP packet hidden inside the GENEVE payload. If the administrator were to click on the VM's vnic, they would only see standard ICMP. By selecting thevmnic0, the administrator captures the traffic as it is placed onto the physical wire, which is the verified location to troubleshoot MTU issues, encapsulation errors, or physical fabric connectivity in a VCF environment.

Comprehensive and Detailed 250 to 350 words of Explanation From VMware Cloud Foundation (VCF) documents:

In aVMware Cloud Foundation (VCF)architecture, theTier-0 Gatewayis the primary point of integration between the virtualized network and the physical world. When dealing with multiple upstream routers (multi-homing), administrators must influence the BGP path selection process to ensure traffic follows the desired path and avoids suboptimal routing or asymmetric flows.

AS-Path Prependis a common technique used to influenceinbound traffic(traffic coming from the physical network into the NSX environment). By repeating its own Autonomous System (AS) number multiple times in the BGP advertisement, the Tier-0 Gateway makes a specific path look "longer" and therefore less desirable to the upstream physical routers. Since BGP prefers the shortest AS-Path, the routers will favor the alternate link that does not have the prepended AS numbers. This is a critical tool in VCF designs to ensure that a primary link is utilized unless a failure occurs.

MED (Multi-Exit Discriminator)is an attribute that suggests to an adjacent external AS which path to take among multiple entry points to the same AS. Like AS-Path Prepend, it influences inbound traffic. A lower MED value is preferred over a higher one. In a VCF environment with multiple Edge Nodes or multiple Tier-0 uplinks, setting different MED values allows the administrator to prioritize specific entry points for traffic entering the SDD

C.  

BFD (Bidirectional Forwarding Detection)is not a BGP attribute; it is a detection protocol used to provide fast failure detection of the link between BGP neighbors. While it triggers faster convergence, it does not influence path selection based on attributes.Costis an OSPF attribute, not a native BGP attribute. Therefore, in the context of NSX Tier-0 BGP configuration, AS-Path Prepend and MED are the verified methods for path manipulation.

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