350-401 Question 90
Single answerAn enterprise network is running Cisco Nexus switches configured with Virtual Port Channels (vPC). The network administrator notices intermittent connectivity issues between two virtual machines (VMs) hosted on separate physical servers connected to the same vPC domain. Upon investigation, it is found that the issue is related to the virtual switching configuration on the hypervisors. What is the most likely cause of this issue?
- A
The vPC domain is not configured with a unique domain ID.
- B
The virtual switch's port-channel hashing algorithm is not aligned with the physical switch's hashing algorithm.
- C
The VMs are incorrectly assigned to different VLANs on the virtual switch.
- D
The virtual switch does not support spanning-tree protocol, causing loops in the network.
Show answer and explanation
Correct answer: B
Explanation
The most likely cause of the intermittent connectivity issue is a mismatch in the port-channel hashing algorithms between the virtual switch on the hypervisor and the physical switch (Nexus) in the vPC domain. This can lead to inconsistent traffic distribution and connectivity issues. Properly aligning the hashing algorithms ensures smooth communication between virtual and physical network components.
- A. Incorrect.
This option refers to the vPC domain configuration on the physical Nexus switches. While an incorrect domain ID could lead to vPC misconfiguration, it does not directly relate to the virtual switching on the hypervisor.
- B. Correct.
If the virtual switch's port-channel hashing algorithm is misaligned with the physical switch's hashing algorithm, traffic distribution could become inconsistent, causing intermittent connectivity issues between the VMs.
- C. Incorrect.
This option refers to VLAN assignment on the virtual switch. While mismatched VLANs could certainly cause communication failure, the issue described in the scenario is intermittent, which is more indicative of load-balancing or hashing inconsistencies.
- D. Incorrect.
Spanning-tree protocol is typically not required or supported on virtual switches, especially in environments where vPC is used, as vPC eliminates loops by design. This is not the root cause of the issue in this scenario.