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Exams300-430Questions#280
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300-430 · Question #280

300-430 Question #280: Real Exam Question with Answer & Explanation

The correct answer is D: Place the primary CMX IP address and the secondary CMX IP address in the same subnet.. Cisco CMX Layer 2 HA requires all three IP addresses - primary, secondary, and virtual - to reside on the same subnet. The primary (192.168.1.4/24) and secondary (192.168.4.4/24) are on different subnets, which breaks Layer 2 adjacency required for HA heartbeat communication.

Question

An engineer configures Cisco CMX. which uses Layer 2 high availability on primary and secondary CMX instances, according to these specifications: - Primary CMX IP address: 192.168.1.4/24 - Secondary CMX IP address: 192.168.4.4/24 - Virtual IP address: 192.168.4.1/24 During testing, the engineer discovers that the failover fails. Which action resolves the issue?

Options

  • APlace the primary CMX IP address and the virtual IP address in the same subnet.
  • BPlace the secondary CMX IP address and the virtual IP address in different subnets.
  • CUse a virtual IP address with CMX Layer 3 high availability.
  • DPlace the primary CMX IP address and the secondary CMX IP address in the same subnet.

Explanation

Cisco CMX Layer 2 HA requires all three IP addresses - primary, secondary, and virtual - to reside on the same subnet. The primary (192.168.1.4/24) and secondary (192.168.4.4/24) are on different subnets, which breaks Layer 2 adjacency required for HA heartbeat communication.

Common mistakes.

  • A. Placing only the primary and virtual IP in the same subnet still leaves the secondary in a different subnet, which does not satisfy the Layer 2 HA requirement that all three addresses share the same subnet.
  • B. The secondary and virtual IP must be in the same subnet for Layer 2 HA to function - placing them in different subnets would further break the configuration, not fix it.
  • C. The question specifically asks about Layer 2 HA; switching to Layer 3 HA changes the architecture entirely and does not address the misconfiguration causing the current failover failure.

Concept tested. Cisco CMX Layer 2 high availability subnet requirements

Reference. https://www.cisco.com/c/en/us/td/docs/wireless/mse/10-6/cmx_config/b_CMX_Configuration_Guide_10_6/b_CMX_Configuration_Guide_10_6_chapter_01110.html

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