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Exams300-365Questions#23
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300-365 · Question #23

300-365 Question #23: Real Exam Question with Answer & Explanation

The correct answer is B: unicast from controller. The WLC mDNS gateway caches Bonjour service advertisements and responds to client queries with unicast replies sourced from the controller itself, rather than forwarding multicast traffic.

Wireless Troubleshooting and Optimization

Question

A network engineer is debugging issues with the mDNS gateway. Which type of reply should be seen in the Wireshark capture when querying for a mDNS service in the Bonjour Cache?

Options

  • Aunicast from Prime Infrastructure
  • Bunicast from controller
  • Cmulticast from devices
  • Dmulticast from controller
  • Eunicast from devices
  • Fmulticast from Prime Infrastructure

Explanation

The WLC mDNS gateway caches Bonjour service advertisements and responds to client queries with unicast replies sourced from the controller itself, rather than forwarding multicast traffic.

Common mistakes.

  • A. Prime Infrastructure does not act as the mDNS responder in the Bonjour gateway architecture - that role belongs to the WLC.
  • C. End devices reply via multicast only in a native mDNS environment with no gateway; a gateway architecture suppresses device-originated multicast replies to clients on other subnets.
  • D. The controller replies via unicast, not multicast - sending a multicast reply would defeat the purpose of the gateway by still flooding the network segment.
  • E. In a gateway deployment the controller answers on behalf of devices, so clients do not receive direct unicast replies from the advertising devices.
  • F. Prime Infrastructure has no role in the mDNS gateway packet flow between clients and the WLC Bonjour cache.

Concept tested. Cisco WLC mDNS Bonjour gateway unicast response

Reference. https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-6/b_mDNS_Solution_guide_8_6.html

Topics

#mDNS gateway#Bonjour#unicast reply#Wireshark

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