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Difficulty: Very hardNetwork Components Roles and Functions

An enterprise network deployment hosts multiple business-critical server workloads on a bare-metal Type 1 hypervisor. The hypervisor is connected via a dual-homed physical 10GbE uplink to an upstream Layer 3 switch. Inside the hypervisor, a internal virtual switch (vSwitch) connects multiple virtual machines (VMs) assigned to VLAN 10. If a virtual machine on VLAN 10 emits an Ethernet broadcast frame (destination MAC FF:FF:FF:FF:FF:FF) during an ARP resolution request, how do these virtual and physical infrastructure components process and scope the broadcast traffic?

  1. The virtual switch forwards the broadcast frame to all other VM virtual interfaces assigned to VLAN 10 on that host and out the physical uplink to the Layer 3 switch, where the switch processes the frame at Layer 2 across VLAN 10 ports but does not forward it across routed Layer 3 boundaries.Answer
  2. B
    The physical Layer 3 switch receives the broadcast frame on its VLAN 10 trunk port and automatically routes it across all active IP subnets and routed interfaces to ensure enterprise-wide resolution.
  3. C
    The Type 1 hypervisor passes the frame to a host operating system kernel driver, which converts the Ethernet broadcast into host OS system calls before writing it directly to the physical NIC ring buffer.
  4. D
    The virtual switch parses the LLDP TLV header inside the ARP payload to determine the physical destination MAC address of the Layer 3 switch and converts the broadcast into a unicast frame.

Answer

The virtual switch forwards the broadcast frame to all other virtual machine interfaces in VLAN 10 and out the physical uplink to the Layer 3 switch, which confines the broadcast within VLAN 10 and does not forward it across Layer 3 routed boundaries.
A Layer 2 virtual switch integrated into a Type 1 bare-metal hypervisor operates as a standard bridge. When a VM issues a broadcast frame, the vSwitch floods it to all vNICs in the same VLAN and out the physical network interface card (pNIC) uplink. Upon reaching the physical Layer 3 switch, the frame is flooded only across ports belonging to VLAN 10. The Layer 3 boundaries on the switch terminate the broadcast, preventing it from reaching other VLANs or subnets.

Step-by-Step Solution

1
Analyze the role and operation of the internal virtual switch (vSwitch) in a Type 1 hypervisor.
The vSwitch acts as a software-based Layer 2 switch operating directly on bare-metal hardware. It maintains a MAC address table per VLAN and floods Layer 2 broadcast frames (FF:FF:FF:FF:FF:FF) to all local vNIC ports in the same VLAN and out physical uplinks.
Virtual switches follow standard IEEE Layer 2 bridging behaviors within configured VLAN boundaries.
2
Evaluate the forwarding behavior of the physical Layer 3 switch upon receiving the broadcast frame over the physical uplink.
The Layer 3 switch floods the broadcast frame to all physical ports participating in VLAN 10 within that Layer 2 broadcast domain, but terminates the broadcast at its Layer 3 switch virtual interface (SVI) or routed interfaces.
Layer 3 boundaries (routers/SVIs) isolate broadcast domains and prevent Layer 2 broadcasts from traversing into other subnets.

Key Concept

Layer 2 Broadcast Domain Scoping in Virtual and Physical Network Components
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Topics

Network Components Roles and Functions

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