Cisco 300-630 Exam Dumps & Practice Test Questions

Question 1:

Based on the exhibit, how does the Cisco ACI fabric handle an ARP request from VM1 when VM2’s location is not yet learned in the fabric?

A. Leaf 101 sends the ARP request directly to one of the proxy VTEP spine switches.
B. The POD1 spine switch replies to the ARP request once its POD1 COOP database learns VM2’s location.
C. Leaf 101 encapsulates the ARP request into a multicast packet addressed to 225.0.37.192.
D. Leaf 101 consumes the ARP reply from VM2 to update its local endpoint database.

Correct Answer: C

Explanation:

In Cisco ACI, when an endpoint such as VM2 is not present in the local endpoint database, the fabric must discover its location to forward traffic correctly. When VM1 sends an ARP request targeting VM2 and VM2 is not yet learned in the fabric, the leaf switch connected to VM1 (Leaf 101 in this case) cannot directly forward the request to a known destination. Instead, Leaf 101 encapsulates the ARP request into a multicast packet destined for the multicast address 225.0.37.192. This multicast address is part of Cisco ACI’s standard unknown destination lookup mechanism.

The multicast packet is then flooded within the fabric to all leaf switches responsible for that subnet, enabling the leaf where VM2 is connected to respond with the MAC address of VM2. This process allows the fabric to dynamically locate the endpoint without prior knowledge of its exact location, thereby maintaining connectivity and efficient endpoint discovery.

Other options are not accurate:

• Option A is incorrect because the ARP request is not specifically forwarded to a proxy VTEP spine. Cisco ACI does not rely on proxy VTEPs for this kind of unknown endpoint forwarding.

• Option B is wrong because spines do not directly reply to ARP requests after COOP (Cisco Overlay Information Protocol) updates; instead, leaf switches handle endpoint lookups and ARP responses.

• Option D describes what happens after the ARP reply is received (local endpoint table update) but does not explain the initial forwarding mechanism of the ARP request itself.

Thus, the correct behavior is described by C, where Leaf 101 encapsulates the ARP request into a multicast packet and floods it within the fabric.

Question 2:

What method does Cisco ACI use to enable forwarding of multidestination packets (such as broadcast, multicast, and unknown unicast) between leaf switches within the same fabric?

A. Associate the VXLAN VTEP addresses with multicast groups.
B. Map VXLAN to the PIM-Sparse Mode multicast protocol.
C. Map the VXLAN Network Identifier (VNI) to a multicast group.
D. Map VXLAN to the PIM-Dense Mode multicast protocol.

Correct Answer: C

Explanation:

Cisco ACI uses VXLAN encapsulation to extend Layer 2 networks across the fabric, and it needs an efficient method to handle multidestination traffic such as broadcast, unknown unicast, and multicast (BUM) packets. The way ACI achieves this is by mapping each VXLAN Network Identifier (VNI) to a specific multicast group.

This mapping allows the fabric to forward BUM traffic to all leaf switches participating in the same VXLAN segment efficiently. When a multidestination packet arrives at a leaf switch, it is encapsulated in VXLAN and sent to the multicast group associated with that VNI. The multicast infrastructure then replicates and delivers the packet to all relevant leaf switches, ensuring all endpoints in the VXLAN segment receive the traffic without unnecessary flooding.

The other options do not accurately describe ACI’s approach:

• Option A incorrectly suggests mapping VXLAN Tunnel Endpoints (VTEPs) to multicast groups. While VTEPs are the endpoints of VXLAN tunnels, the multicast group association is done with the VNI, not directly with VTEPs.

• Options B and D mention PIM-Sparse Mode and PIM-Dense Mode protocols, which are multicast routing protocols used in traditional IP multicast environments. Cisco ACI does not rely on these PIM protocols for VXLAN multicast traffic forwarding within the fabric; it uses a native VXLAN multicast mapping mechanism instead.

Therefore, the correct answer is C, where the VXLAN VNI is mapped to a multicast group to efficiently manage multidestination traffic inside the ACI fabric.

Question 3:

What benefit does the VXLAN source port provide to overlay packet forwarding when it uses a hash derived from the inner packet’s Layer 2, Layer 3, and Layer 4 headers?

A. Equal-Cost Multi-Path (ECMP) forwarding
B. TCP performance optimization
C. Disabling fragmentation
D. Support for jumbo frames

Correct Answer: A

Explanation:

In a VXLAN (Virtual Extensible LAN) environment, encapsulation adds an outer header around the original (inner) packet. To efficiently forward these overlay packets across the underlay network, VXLAN uses a hashing mechanism based on the inner packet headers — specifically from Layer 2 (Ethernet), Layer 3 (IP), and Layer 4 (TCP/UDP) fields. This hash influences the source port selection for UDP encapsulation.

The key purpose of this hashing is to enable Equal-Cost Multi-Path (ECMP) routing, which is the ability to distribute network traffic evenly across multiple paths that have the same cost metric. By hashing multiple header fields, VXLAN ensures that packets belonging to the same flow consistently follow the same path, preventing packet reordering which can degrade application performance. This consistent hashing supports efficient load balancing across several equal-cost links, enhancing both network reliability and throughput.

Option A is correct because the VXLAN source port hash directly enables ECMP forwarding, allowing the network to leverage multiple equal-cost paths dynamically for optimal traffic distribution.

Option B is incorrect since TCP optimization involves protocol-level enhancements like window scaling or congestion control, which VXLAN source port hashing does not affect.

Option C is also incorrect as fragmentation is related to packet size and MTU handling, not to the hashing of packet headers.

Option D refers to jumbo frames, which allow larger Ethernet frames than standard sizes. While VXLAN supports larger frames due to encapsulation, the source port hash itself does not provide jumbo frame functionality.

In summary, the VXLAN source port’s use of the inner packet’s header hash primarily facilitates ECMP, enabling efficient multi-path forwarding and enhanced network performance in VXLAN overlays.

Question 4:

Which two configurations are Cisco’s recommended best practices for setting up NIC teaming load balancing on Cisco UCS B-Series blades connected to Cisco ACI leaf switches? (Choose two.)

A. Implement vPC+
B. Enable LACP in active mode
C. Use PAgP for aggregation
D. Create a vPC
E. Enable MAC pinning

Correct Answer: B, D

Explanation:

When configuring NIC teaming load balancing for Cisco UCS B-Series servers connected to Cisco ACI leaf switches, following Cisco best practices ensures high availability, efficient load distribution, and fault tolerance.

Option B (Enable LACP active mode) is essential because LACP (Link Aggregation Control Protocol) actively negotiates the link aggregation between the UCS blades and the ACI leaf switches. LACP in active mode allows both ends to initiate and respond to aggregation protocol messages, ensuring that the link aggregation group (LAG) is properly formed and maintained dynamically. This dynamic negotiation facilitates optimal load balancing and failover capabilities.

Option D (Create a vPC) is also a best practice within Cisco ACI environments. vPC (Virtual Port Channel) allows multiple physical links from the UCS blades to be aggregated and connected to two separate leaf switches, creating a single logical port channel. This setup prevents loops without the need for Spanning Tree Protocol and increases bandwidth availability. It also provides fault tolerance and load balancing across the physical links, improving network performance and reliability.

Option A (vPC+) is an advanced Nexus feature used primarily in multi-fabric or more complex Nexus environments but is not the standard best practice for UCS B-Series to ACI connections.

Option C (PAgP) is an older Cisco proprietary protocol for link aggregation but is not recommended in modern environments where LACP is the preferred standard due to wider interoperability and better support.

Option E (MAC pinning) is generally used for static MAC-to-port binding in virtualized environments, not recommended for NIC teaming load balancing in this UCS-to-ACI context.

In conclusion, enabling LACP active mode and creating a vPC are the Cisco best practices for NIC teaming load balancing on UCS B-Series blades connected to ACI leaf switches, ensuring dynamic link aggregation, load balancing, and redundancy.

Question 5:

An organization migrates its virtual machines to Cisco ACI. VM1 is mistakenly connected to the PortGroup IT|3TierApp|Web. 

Which configuration action should be taken on Bridge Domain BD1 to restrict IP address learning from this misattached VM?

A. Enable Enforce Subnet Check
B. Enable Rogue Endpoint Control
C. Enable GARP-based Endpoint Move Detection Mode
D. Disable Remote Endpoint Learning

Correct Answer: A

Explanation:

In Cisco ACI, managing endpoint learning within Bridge Domains (BDs) is essential to maintain proper network segmentation and security. When a virtual machine (VM) such as VM1 is incorrectly connected to a PortGroup that maps to the wrong BD—here BD1—it can cause incorrect IP address learning. This mislearning can lead to traffic being forwarded inappropriately, potentially causing security or connectivity issues.

The key to controlling this behavior is to ensure that endpoints can only be learned if they belong to the correct subnet associated with that BD. Enabling Enforce Subnet Check accomplishes this by verifying that the IP addresses learned in the BD belong within the subnet range defined for that BD. If VM1's IP address does not match the subnet configured for BD1, the switch will reject its IP learning, effectively preventing VM1 from communicating through that BD. This action confines IP learning strictly to authorized subnets and blocks improperly attached VMs from impacting the network.

Option B, Rogue Endpoint Control, is designed to detect and quarantine unauthorized or rogue devices appearing in the network. While it offers endpoint security, it doesn’t specifically restrict IP address learning within a BD, so it’s less applicable for this scenario.

Option C, enabling GARP-based Endpoint Move Detection, helps detect when an endpoint moves from one port to another using Gratuitous ARP messages. It focuses on endpoint mobility but does not limit IP address learning or prevent incorrect endpoint placement.

Option D, disabling Remote Endpoint Learning, restricts learning of endpoints from remote leaf switches, which is useful in certain topologies but does not address misconfigured VMs within the local BD.

Therefore, enabling Enforce Subnet Check is the correct solution to limit IP address learning in BD1 and prevent misattached VMs like VM1 from disrupting the network.

Question 6:

In the given scenario, what configuration is required to allow the Policy-Based Routing (PBR) node (LB-int) to track the availability of the endpoint residing in the EPG server?

A. Endpoint Dataplane Learning
B. Disable Unicast Route for Client and Server Bridge Domains
C. PBR Node Tracking
D. Direct Connect in the Service Graph Template

Correct Answer: C

Explanation:

Policy-Based Routing (PBR) enables granular control over how traffic is routed based on policies rather than relying solely on destination IP prefixes. When implementing PBR in Cisco ACI environments, the PBR node—here identified as LB-int (likely a load balancer or similar device)—must be aware of the availability status of endpoints it routes traffic to. This dynamic knowledge allows the PBR node to avoid sending traffic to unreachable or down endpoints, maintaining service reliability.

To achieve this, PBR Node Tracking is configured. This feature lets the PBR device monitor the health or reachability of endpoints within the Endpoint Group (EPG) it serves. If the endpoint becomes unavailable, the PBR node can adjust its routing decisions accordingly, rerouting traffic or triggering failover as dictated by policies. This tracking ensures traffic is only directed to operational endpoints, optimizing performance and resilience.

Option A, Endpoint Dataplane Learning, involves the discovery and mapping of endpoints on the data plane. While this helps build endpoint databases, it doesn’t provide real-time health or availability tracking for PBR purposes.

Option B, disabling unicast routing in client and server bridge domains, concerns route advertisement and forwarding behaviors but does not facilitate the monitoring of endpoint health or availability by the PBR node.

Option D, Direct Connect in the service graph template, relates to establishing service chains or connectivity between devices but does not provide the capability to monitor endpoint status for routing adjustments.

In summary, configuring PBR Node Tracking enables the PBR device LB-int to monitor endpoint availability dynamically and make intelligent routing decisions, ensuring effective traffic management within the Cisco ACI fabric.

Question 7:

An engineer wants to restrict both local and remote endpoint learning strictly to the subnet of the bridge domain within Cisco APIC. What configuration should be applied?

A. Turn off Remote Endpoint Learning
B. Activate Enforce Subnet Check
C. Disable Endpoint Dataplane Learning
D. Enable Limit IP Learning to Subnet

Correct Answer: D

Explanation:

In a Cisco ACI environment, endpoint learning refers to the process by which the fabric identifies and keeps track of the endpoints (EPs) attached to the network. Sometimes, network engineers need to ensure that endpoint learning is limited only to the IP addresses within the subnet of the bridge domain to maintain security and proper segmentation.

The correct approach here is to enable the “Limit IP Learning to Subnet” option in the Cisco APIC configuration. This setting restricts both local and remote endpoint learning exclusively to the subnet defined for the bridge domain. This means endpoints with IP addresses outside the subnet are not learned or propagated, which enforces stricter boundary control.

Option A (Disable Remote EP Learn) disables the learning of endpoints from remote leaf switches but does not restrict local endpoint learning nor guarantees subnet enforcement. This only partially limits learning and doesn’t fully address the requirement.

Option B (Enable Enforce Subnet Check) is related to validating endpoint IP addresses against the subnet but does not directly restrict endpoint learning to that subnet. It’s more of an IP verification mechanism than a learning boundary enforcer.

Option C (Disable Endpoint Dataplane Learning) completely disables the learning of endpoints via the data plane, which is an overly broad action and not what is required here. The goal is to limit learning, not to stop it altogether.

Therefore, option D is the precise and recommended action. It ensures that the fabric only learns endpoints that reside within the defined bridge domain subnet, which is critical for maintaining proper network segmentation and security within the Cisco ACI fabric.

Question 8:

What is the function of the Forwarding Tag (FTAG) within Cisco ACI?

A. FTAG labels iVXLAN traffic to enforce policies in the fabric
B. FTAG adds a label to VXLAN traffic for policy enforcement
C. FTAG trees are used to balance unicast traffic within the fabric
D. FTAG trees provide load balancing for multi-destination traffic

Correct Answer: D

Explanation:

In Cisco ACI, the Forwarding Tag (FTAG) is a fundamental element of the fabric's traffic handling, particularly for multi-destination traffic such as multicast and broadcast. The ACI fabric uses an integrated VXLAN (iVXLAN) overlay to encapsulate traffic, and FTAGs are utilized within this mechanism to optimize forwarding efficiency.

The primary role of FTAG is to enable the fabric to load balance multi-destination traffic by building FTAG trees. These trees help distribute multicast and broadcast traffic across multiple paths in the fabric, improving bandwidth utilization and ensuring that traffic is efficiently forwarded to all intended recipients without creating bottlenecks.

Option D is correct because FTAG trees are explicitly designed to support this multi-destination traffic load balancing, which is critical in scalable and high-performance fabrics.

Option A and B are incorrect because although FTAGs relate to iVXLAN traffic, their function is not to apply policy labels but to handle traffic forwarding and load balancing. Policy enforcement in ACI typically uses other mechanisms and tags.

Option C is wrong since unicast traffic forwarding in ACI follows different forwarding paths that do not require FTAG trees. FTAG specifically handles multicast and broadcast traffic, which require special distribution trees.

In conclusion, FTAG is crucial for efficiently distributing multi-destination traffic in Cisco ACI, making D the right choice.

Question 9:

In an Ethernet Virtual Circuit (EVC) setup, what is the required Spanning Tree Protocol (STP) mode when multiple bridge domains are configured?

A. RSTP or PVST+ must be used
B. Each bridge domain must be assigned to a separate VLAN
C. MSTP is the required STP mode
D. Bridge domains must be assigned to different MST instances

Correct Answer: C

Explanation:

In an Ethernet Virtual Circuit (EVC) environment where multiple bridge domains are configured, the Spanning Tree Protocol (STP) plays a vital role in preventing loops and managing path redundancy. However, not all STP modes are suitable for handling multiple bridge domains efficiently.

The correct STP mode in this context is MSTP (Multiple Spanning Tree Protocol). MSTP allows multiple VLANs and bridge domains to be grouped into a smaller number of spanning tree instances. This grouping enhances scalability by reducing the number of STP instances the network needs to run and improves network efficiency by allowing different VLAN groups to have different spanning tree topologies.

Option C is correct because MSTP was designed to handle complex environments with numerous VLANs and bridge domains. It supports multiple spanning trees mapped to various VLANs, enabling better resource utilization and traffic management.

Option A is incorrect since RSTP (Rapid STP) and PVST+ (Per VLAN STP) are either limited to single spanning tree instances or per-VLAN instances, which can become unmanageable and less efficient when many bridge domains exist.

Option B is a partial truth because while bridge domains often correspond to VLANs, simply assigning bridge domains to different VLANs does not address the fundamental STP mode required for loop management.

Option D is incorrect because bridge domains do not have to be in different MST instances. They can be grouped in the same MST instance for better management, as MSTP supports VLAN-to-instance mappings flexibly.

In summary, MSTP is the recommended STP mode for Ethernet Virtual Circuit environments with multiple bridge domains because it provides scalable, efficient spanning tree management. This makes option C the best choice.

Question 10:

Within an MPLS Point-to-Multipoint Traffic Engineering (P2MP TE) network, which type of router can function both as an intermediate (midpoint) and an endpoint (tailend) router?

A. Headend router
B. Source router
C. Transit router
D. Bud router

Correct Answer: D

Explanation:

In MPLS Point-to-Multipoint Traffic Engineering (P2MP TE) networks, routers play distinct roles in forwarding traffic from the source to multiple destinations efficiently. Understanding these roles is critical for designing and troubleshooting MPLS P2MP networks.

The bud router is a unique type of router that can serve dual functions: as an intermediate node within the P2MP path (midpoint) and as an endpoint for some branches (tailend). The term “bud” refers to a branching point where traffic coming from the headend or source router is split toward multiple downstream routers.

Option D is correct because the bud router acts as both a branching node—relaying traffic further into the network—and as an endpoint for certain traffic streams where the distribution ends.

Option A (Headend router) is incorrect because the headend router is the origin of the MPLS P2MP traffic. It initiates the traffic but does not function as an intermediate or tailend router.

Option B (Source router) is essentially another term for the headend router and serves the same role: originating traffic, not relaying or terminating it.

Option C (Transit router) is responsible for passing traffic along the network path but only acts as a pure relay. It does not serve as an endpoint where traffic flow terminates, so it cannot be a tailend router.

To conclude, the bud router’s role as both midpoint and tailend makes it essential for efficient MPLS P2MP TE networks, enabling traffic branching and termination within the same device. Thus, option D is the correct answer.