VMware 3V0-25.25 Exam Dumps Questions and Answers

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

In aVMware Cloud Foundation (VCF)environment, particularly with the high-performance requirements of North-South routing,BGPandBFD (Bidirectional Forwarding Detection)are used in tandem to ensure rapid failure detection. A common but subtle issue in fresh or modified environments is anMTU (Maximum Transmission Unit) mismatchon the physical or virtual uplinks.

When BGP establishes a neighborship, it initially exchanges small keepalive packets. These small packets easily pass through interfaces even if there is an MTU mismatch (e.g., the Edge is set to 9000 bytes but a physical switch in the path is limited to 1500 bytes). However, once the BGP state reaches "Established," the routers begin exchanging full routing tables. TheseBGP Updatepackets are often large and will be fragmented or dropped if they exceed the MTU of any hop in the path.

The symptom described—where the session is stable for a few minutes (during the initial handshake) and then flaps—is the hallmark of an MTU issue. The "Detect Time Expired" diagnostic in BFD occurs because the BGP hold timer expires when it fails to receive the large update packets, or the BFD packets themselves are delayed/lost due to the congestion caused by retrying large, failed transmissions. According to VMware NSX troubleshooting documentation, if pings (small packets) succeed but the BGP session fails specifically when traffic load or route counts increase, the MTU should be the first setting verified.

VCF 9.0 and 5.x designs mandate consistent MTU settings (typically9000 MTUfor the overlay and at least1500+for the uplinks) across the entire path, including the virtual switch (VDS), the Edge VM vNICs, and the physical ToR switches. A mismatch here prevents the completion of the BGP state machine's full synchronization, leading to the cyclic "flapping" observed by the administrator.

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

NSX Federationis the architectural framework used withinVMware Cloud Foundation (VCF)to provide consistent networking and security across multiple sites. The core of this framework is the relationship between theGlobal Manager (GM)and one or moreLocal Managers (LMs).

The registration process is the critical first step in establishing this "parent-child" relationship. According to the "NSX-T Data Center Administration Guide" and Federation-specific documentation, the registration is initiated from theActive Global Manager.

Initiation and Credentials (Requirement E):The administrator logs into the Global Manager UI and navigates to the "System > Fabric > Locations" section. To add a new site, the GM-Active requires theIP address or FQDNof the target Local Manager and theAdmin credentials. This allows the GM to authenticate with the LM, exchange security certificates, and establish a secure thumbprint-verified connection.

Stable Communication Endpoint (Requirement C):For the ongoing management and synchronization of "Global Objects" (like Tier-0s or Security Groups), the GM must communicate with the LM cluster as a whole rather than a single individual node. Therefore, theLM Cluster Virtual IP (VIP)or aFQDNpointing to that VIP is provided. Using the VIP ensures that if the specific LM node that initially handled the registration fails, the GM can continue to communicate with the remaining nodes in the LM cluster without administrative intervention.

Option A is incorrect because the Global Manager typically manages the licensing for the federation, not the LM validating the GM. Option B is incorrect as an external load balancer is not a prerequisite for the native GM-LM registration handshake. Option D is incorrect because providing the IP of an individual node (one of the three) does not provide the high availability required for a production Federation environment. Thus, the use of theCluster VIPand theGM-Active's request for LM credentialsare the verified procedural requirements.

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 SDDC.

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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