Cisco 300-540 Exam Dumps

In a VXLAN BGP EVPN Multi-Site environment:

DCI tracking monitors the health of the DCI links. If all DCI-tracking interfaces go down, the leaf can incorrectly keep advertising or learning remote MAC/IP reachability, leading to packet loss and sub-optimal forwarding for servers in that VLAN/L2VNI.

For proper operation, each DCI-facing interface must be enabled with evpn multisite dci-tracking so that the Multi-Site border leaf tracks reachability over that link.

When using EVPN Multi-Site, BUM (broadcast, unknown unicast, multicast) traffic toward remote sites is typically handled via ingress replication, not multicast groups, for each L2VNI participating in Multi-Site. The configuration snippet shows an L2VNI (vn-segment 16535) still mapped to mcast-group 239.1.1.0, which is inconsistent with Multi-Site recommendations and contributes to packet loss.

Therefore, to fix the problem:

Enable DCI tracking on the uplink:

interface Ethernet1/1

evpn multisite dci-tracking

This restores proper DCI-link state monitoring for Multi-Site. Option C

Change the L2VNI behavior from multicast to Multi-Site ingress replication:

Under the VNI for VLAN 11, configure:

evpn

vni 16535 l2

multisite ingress-replication

or the equivalent command for the specific NX-OS release, thereby aligning the L2VNI with EVPN Multi-Site design and eliminating packet loss. Option D

Options A and B are ELAM (embedded logic analyzer) filters used only for packet capture and do not resolve the forwarding issue. Option E is an ACL line unrelated to EVPN VXLAN or DCI tracking and does not address the underlying problem.

Cisco Umbrella DNS-layer security:

Blocks malicious domains used in phishing, malware, C2 communications, and ransomware

Stops threats before connections are made

Uses DNS-based filtering and threat intelligence

It does not mitigate:

DDoS (needs scrubbing centers)

Brute force login attempts

Zero-day exploits directly

Thus, A is correct.

Comprehensive and Detailed Explanation

Cisco NFVIS logging levels (from lowest to highest):

critical

error

warning

info

debug highest verbosity

To capture maximum diagnostic detail, engineers must enable debug logging on the operational log type, which records system activity and runtime behavior.

Thus the correct command is:

system set-log logtype operational level debug

This provides the deepest troubleshooting visibility.

In a cloud-scale or data center--scale environment, Virtual Extensible LAN (VXLAN) is used as an overlay technology to transport Layer 2 segments over a Layer 3 underlay network. VXLAN encapsulates Layer 2 Ethernet frames inside UDP/IP packets, allowing broadcast, unknown unicast, and multicast (BUM) traffic and tenant Layer 2 domains to be extended across a routed IP fabric.

Key points aligned with Cisco Service Provider Cloud Infrastructure design principles:

VXLAN creates a Layer 2 overlay on top of a Layer 3 underlay.

The VXLAN Network Identifier (VNI) provides a much larger segmentation space than traditional VLANs, enabling multi-tenancy at cloud scale.

Because the underlay is pure Layer 3 (IP routed fabric), VXLAN allows you to interconnect Layer 2 segments between leaf switches or data centers over an IP/MPLS backbone without relying on large Layer 2 domains in the physical network.

Why the options evaluate as follows:

Option A: extends Layer 2 segments across the underlying Layer 3 infrastructure

This is the core benefit of VXLAN in cloud-scale designs. VXLAN encapsulates Layer 2 frames into IP/UDP headers, allowing isolated Layer 2 segments (per VNI) to be stretched across a routed IP network. This enables:

Multi-tenant Layer 2 connectivity across a distributed cloud fabric

Mobility of virtual machines or containers while keeping same IP/MAC addressing

Use of an IP-based leaf--spine or service provider underlay for scalability and resiliency

Option B: extends Layer 3 segments across the underlying Layer 2 infrastructure

This is the opposite of what VXLAN does. VXLAN is explicitly L2-over-L3, not L3-over-L2. Extending pure Layer 3 segments over Layer 2 is not the VXLAN use case.

Option C: reduces spanning-tree complexity across the Layer 2 infrastructure (Partially related but not the primary or direct benefit)

In modern designs, the underlay is Layer 3 routed, and VXLAN overlays provide logical Layer 2 segments. This design avoids dependence on spanning tree in the fabric, which indirectly reduces STP complexity. However, the fundamental, exam-relevant benefit is L2 extension over L3, so C is not the best or most accurate answer compared to A.

Option D: eliminates the need for a Layer 3 underlay in the service provider infrastructure

VXLAN absolutely requires an IP (Layer 3) underlay for transport. VXLAN tunnels are built over a routed infrastructure (leaf--spine, MPLS/IP core, etc.). It does not remove the need for Layer 3; it depends on it.

For a site-to-site IPsec VPN, each peer must configure a pre-shared key tied to the public IP address of the remote VPN peer:

crypto isakmp key <KEY> address <REMOTE_PUBLIC_IP>

From the diagram:

R1 outside IP: 192.168.10.1/24

R2 outside IP: 192.168.20.2/24 remote peer for R1

In the current R1 configuration, the ISAKMP key is incorrectly bound to 192.168.10.2, which is a local next-hop/ISP address on R1's own subnet, not the R2 public IP. Because the pre-shared-key address does not match the source IP of R2's IKE packets, phase 1 negotiation fails and the tunnel never comes up.

The correct configuration on R1 must therefore be:

crypto isakmp key vpnuser address 192.168.20.2

Options A and C incorrectly change the default route (next hop must be the local ISP router, not R2's public IP or a LAN address). Option D uses an internal address (10.1.1.2), which is not the IP used for IKE on the Internet.