Multicast Domain Call System (mDNS)– Still Flooding?


” More than likely”, stated John with disappointment and misery as he faced the complicated task of stabilizing the efficiency of a large university network while at the same time supporting Multicast Domain Name System (mDNS) services for end-users. The requirement to accommodate non-routable mDNS technology throughout complex business networks is a frequent difficulty. John’s worries, such as high CPU usage, WiFi network instability, extensive mDNS flooding, and the requirement to re-structure the Layer 2 network, are simply a few of the well-documented difficulties that arise in any large, inundated enterprise network environments.

In today’s busy and ever-evolving technological landscape, digital natives expect seamless access to a vast array of services with just a few easy taps or clicks. They anticipate the exact same level of convenience and ease of usage in your home and at work, which has actually set a high bar for enterprise networks to meet. The mDNS procedure has proven to be an indispensable tool for delivering abundant, instinctive service experiences to end users. As an outcome, it has become a widely embraced and de facto requirement for “smart” customer devices, Web of Things (IoT) gadgets, and audio-visual (AV) endpoints.

As technology continues to advance, the application of Bring Your Own Device (BYOD) policies has given way to the proliferation of next-generation information technology (IT), operational innovation (OT), and audio-visual (AV) handled products that include mDNS protocols. This can posture considerable obstacles for network architects like John, as they must navigate the intricacies of supporting such requiring and mission-critical services while guaranteeing scalability, security, and non-disruptive network operation.


The RFC 6762 presented mDNS to support zero-configuration networking abilities, which significantly simplified peer-to-peer service management with no brand-new knowing curves, add-on apps, or classic tools– it just works. The procedure, designed to operate in single flat Layer 2 networks, provides transparent and smooth functionality to end-users, making it a perfect suitable for house networks. Nevertheless, such innovations likewise present a broad series of challenges for IT experts, as they should firmly link services between disparate networks while implementing granular security policies, figuring out location distance, appointing user roles, and much more. John misses the AppleTalk Routing that he utilized to use, as the market decoupled service routing from IP routing a number of years earlier. And when John can’t route mDNS services throughout the university school, the only option left was to extend the mDNS flood to a central Wireless LAN Controller (WLC).

Keep in mind– “Routing-on-Stick“? Due to the lack of service routing, the Enterprise network adopted the “Service-On-Stick” model to bridge disjointed mDNS endpoints between Wired and Wireless networks across the IP core. The Cisco WLC acted as the one-arm-mDNS-gateway function, which needed IT to extend the mDNS flood from Wired networks to discover services from remote Wired networks and proxy or distribute them to Wireless users on an on-demand basis. As the size and style of Enterprise networks differ, so does the “Service-On-Stick” deployment mode, which can work based on the mDNS flood-n-learn method, as highlighted in Figure 1 below.

As the size and design of Enterprise networks varies, so does the Figure 1: mDNS Flood-n-Learn Wired/Wireless Networks The Impact The flood-and-learn-based technology in flat Layer 2 networks runs stealthily without the need for IT involvement. Nevertheless, this can be a cause for issue for IT organizations as these innovations can circumvent Infosec policies and negatively affect the performance of higher-level systems, networks, and endpoint

gadgets. The Enterprise IT demands essential concerns to be asked regarding the deployment mode of “Service-on-Stick” using mDNS:

Does it work?

Undoubtedly. The BYOD period has actually conclusively demonstrated the effectiveness of this traditional method. All the Figure-1 flood-and-learn release techniques stay legitimate and relevant, similar to the “Routing-on-Stick” configuration which is still extensively made use of today. Nonetheless, when the WLC necessitates Layer 2 extension through several hops away from the wired mDNS provider endpoints, such as AirPlay-enabled devices, AV systems, and printers, the service context is lost, resulting in an absence of connectivity, security policy enforcement, and schedule synchronization across the network in real-time. This can lead to numerous recognized constraints, such as bad end-user service browsing and a suboptimal usability experience.

Can it scale?

The concern of scalability is vital. Regardless of mDNS, the basic networking design principles advocate for a routing-based approach, with bridging used only as a last option. As networks, endpoints, and mDNS services expand in a multitudinous way, any main processing innovation on any single networking device may present various abnormalities, therefore raising the threat of total system failure once it exceeds its functional limitations.

It’s not simply the network scale. Making use of a tool like Wireshark and filtering for mDNS traffic within a single VLAN on your computer can supply important insights into the mDNS traffic load. This alone can be a considerable contributing aspect to network resource deficiency, CPU utilization, sluggish application performance, and battery drain on each connected endpoint. Furthermore, it’s important to think about the impact on network bandwidth, CPU/memory use, and overall network stability while examining the performance of mDNS.

Is it secure?

As enterprise networks embrace a Zero Trust security design to secure their infrastructure, implementing service-level stringent info security policies in flooded Layer 2 networks might prove to be an overwhelming task. This might lead the IT organization to resort to completely blocking mDNS traffic, which may have a damaging impact on different business-critical applications. Security policy enforcement is limited to the main WLC, making it imperative to consider alternative security procedures to reduce potential risks.

The 2X Effect

The next-generation enterprise networks are promptly developing from traditional Spanning Tree Procedure (STP) or overlay networks to advanced fabric-based technologies such as Virtual Extensible LAN (VXLAN). These options use greater flexibility to IT companies, allowing them to create non-blocking Layer 2 networks or establish segmented Layer 3 overlay networks. Nevertheless, as the Layer 2 network border expands throughout the enterprise IP core network, the mDNS flood border also expands, accidentally. In the shared broadcast domain, service-level division to limit mDNS discovery might jeopardize network security, making it vital to evaluate the potential security dangers and carry out suitable measures to mitigate them.

To attend to the possible unfavorable results on network performance and security that can be caused by mDNS applications, different IT techniques are often executed, such as filtering mDNS traffic at the network edge, executing rate-limiting on CPU use or user interfaces, and so on. These measures focus on keeping network stability and security over accommodating mDNS services. In specific situations, nevertheless, it may not be possible to completely reduce these impacts. For example, in next-generation immersive meeting areas, it may be required to make use of Cisco Webex AirPlay for content sharing at the swipe of a finger. Similarly, convention centers may need advanced Audio-Video solutions, and making centers may depend on over-the-air portable radio programming to efficiently manage their large-scale operations.

Cisco DNA Service for Bonjour

IP routing is specifically developed to restrict flood boundaries to the edge of a network. Utilizing a smart routing protocol control-plane, it allows the creation of a hierarchical and scalable infrastructure that can integrate network states, impose security measures, and supply end-to-end reachability to each connected endpoint. Likewise, the Cisco DNA Service for Bonjour option is constructed on these principles, providing an end-to-end scalable and protected solution for routing mDNS services in enterprise-grade Wired and Wireless networks.

The Cisco DNA Service for Bonjour is an important option to a long-standing problem in IT– the integration of mDNS services seamlessly without necessitating major changes to existing running environments, all while keeping strict security requirements. Figure 2 highlights the end-to-end Cisco DNA Service for Bonjour option architecture for a conventional business campus network.

Local Area and Wide Area Bonjour benefits: hierarchical, secure, location-aware, increased performance, improved battery life Figure 2: Cisco DNA Service for Bonjour Option The Cisco DNA Service for Bonjour provides a comprehensive solution that successfully addresses different classic

  • WLC flood-n-learn mDNS network obstacles by providing: End-to-End Service– An enterprise-grade service discovery and circulation that eliminates mDNS flood and makes it possible for unicast-based wired and cordless networks without any network border restrictions. The IT experts can effortlessly integrate solutions without forklift design modification to support end-to-end service-oriented business networks.
  • Scalability– A completely dispersed mDNS service-routing solution that decouples classic and centralized mDNS processing on WLC systems, resulting in an extremely scalable and trusted option that can handle a great deal of devices and services, even in big and complex networks.
  • Security– Providing business IT organizations control over brand-new services based upon place, role, and other policies, the brand-new unicast-based model, hence implicitly rejecting un-checked or out-of-policy services based on IT-enforced policies, ensuring that the network is secured from prospective security dangers and vulnerabilities.
  • User Experience– The end-user service discovery and circulation experience stay intact in between residential and protected business networks, with a no learning curve and an agent-less mDNS service-routing service, allowing IT to easily adapt brand-new services presented in consumer products as they develop without the requirement for major changes to the network infrastructure. This results in a seamless and efficient network experience for end users.
  • Overall, the Cisco DNA Service for Bonjour option supplies business IT companies with a robust, protected, and scalable solution that can meet the growing demands of their network facilities and expand new mDNS services required by business-critical endpoints, increase performance on consumer items, and more.

    Enterprise-Grade mDNS Option

    The Cisco DNA Service for Bonjour is an extremely versatile and versatile mDNS service-routing service that can be carried out in a wide variety of standard or contemporary fabric-based network architectures. The solution allows Business IT organizations to efficiently transition from a flood-and-learn technique (Figure 1) to a totally unicast-based mDNS service-routing design. Depending upon the particular Wired and Wireless network style, the mDNS flood-boundary can end at the first-hop Layer 2 Ethernet switch or WLC for policy enforcement and service routing to the upstream L2/L3 network.

    The unicast-based service routing between Cisco Driver 9800 WLC, Driver 9000 switch, or Cisco DNA Center requires just vital IP connectivity and runs independently of other IP routing procedures. The implementation of a multicast routing protocol in the Wired and central-switching Wireless user network is optional. The new Cisco IOS XE 17.9.1 software application on Driver 9800 WLC introduces the AP Multicast and Wireless user Switched Virtual Interface (SVI) user interface as optional when WLC is configured in “mDNS Service Peer” mode.

    mDNS Flood-Free Wired/Wireless Traditional Networks

    Figure 3: mDNS Flood-Free Wired/Wireless Traditional Networks Hierarchical mDNS Service-Routing The well-established style principles of structure and hierarchy are extremely efficient when planning and building extensive Enterprise campus networks. These concepts use versatility, modularity, and scalability, whether used to physical cabling, identifying L2/L3 boundaries and more. The Cisco DNA Service for Bonjour service complies with these same concepts by managing mDNS limits between two-tier hierarchical service-routing domains, ensuring a robust and efficient network facilities:

    City Bonjour Domain

    Path mDNS even in bridge network (traditional or overlay). When several Driver 9000 household switches or WLCs in Layer 2 mode link to a typical Circulation IP gateway, it is referred to as a City Bonjour Domain. The IGMP Snooping was purpose-built to fix IP Multicast traffic flood obstacles in the Layer 2 network environment. In flood-free unicast-based Layer 2 Wired and Wireless networks, the IT gets full mDNS security control to procedure and route services following policies:

    • Gain access to: Each Layer 2 switch OR WLC terminates mDNS flood from LAN port or AP to locally process mDNS info based on IT-defined policies. Carries out service routing with the upstream IP gateway in Distribution.
    • Circulation: Discovers mDNS service circumstances or demands from downstream Layer 2 Change or WLC and optionally distributes between them if required.

    The switch performs inter-VLAN local routing without the need for configuring any IP routing protocol, thus providing an effortless experience for network administrators. Similarly, in the Local Area Bonjour domain, the mDNS service-routing between mDNS Wired and Wireless users is confined within the same Layer 2/3 network boundary, thus the use of Cisco DNA Center is optional.

    Wide Area Bonjour Domain When mDNS services require to be found beyond a single IP entrance, the Cisco Wide Area Bonjour option is required. Like the client-server design, the network-wide dispersed Catalyst 9000 IP entrance switch develops unicast-based service routing with the centralized Cisco DNA Center hosting the Wide Location Bonjour application. The IT-defined international service-routing policy on Cisco DNA Center allows service-routing between IP gateway switches, providing a scalable and The switch requires IP routing protocols to discover remote network routes. Similar to an Interior Border Gateway Protocol (i-BGP), the Route Reflector discovers and disseminates BGP prefixes. Analogously, the Cisco DNA Center discovers and disseminates mDNS services between IP/mDNS gateways based on the global service policy, providing a comprehensive and organized approach to managing mDNS services across the network.

    efficient solution for managing mDNS services throughout a Wide Location Bonjour domain. The unicast information path between the IP gateway follows routing tables and policies. The Cisco DNA Center is never ever in the data path in between IP gateways. Distance Matters Imagine you remain in front of a printer and your 10.9-inch iPad dynamically finds hundreds of them, however the one you need is evasive and can not lie or looked for within the interface. The efficiency of employees is impeded in Business networks when innovation stops working to supply optimum user experience in service navigation and usability. In standard flood-and-learn-based networks, the existence of the company and receiver can not be properly recognized and propagated across the network. Using disparate network mappings using wireless radios offers restricted to no efficient service.

    If the network can route mDNS services, it can likewise route area distances. The Cisco DNA Service for Bonjour uses flexibility in specifying and building “service zones” by just tagging and organizing Ethernet switch LAN ports and Wireless Access Points (APs) on a WLC into typical service policy zones. The iPad now discovers a narrowed-down set of printers based on the IT-defined location-based service policy. As an iPad user moves around floorings and structures, the distance guidelines are instantly adjusted, offering a seamless, “home-like” zero-configuration service experience in Enterprise network environments of any size.

    Support Matrix

    The Cisco DNA Service Bonjour service is a thorough, end-to-end Business networking service that empowers our clients to build safe and secure and expandable mDNS service-routing networks using Cisco’s extensive Ethernet changing and Wireless networking portfolio.

    The versatile routing architecture is compatible with a variety of standard L2/L3 networks, MPLS, and innovative fabric-based networks such as Cisco SD-Access and BGP EVPN VXLAN. As portrayed in Table 1, the Cisco DNA Service for Bonjour assistance matrix highlights the different abilities of this ingenious option.

    Cisco DNA Service for Bonjour support matrix illustrates the various capabilities of this innovative solution. Table– 1: Cisco DNA Service for Bonjour Support Matrix Key Takeaway John accomplished the job of moving his 60th and final University building with Wide Location Bonjour, resulting in a completely mDNS flood-free network. The totally distributed mDNS processing across LAN switches and central WLC contributes to a significant increase in the system, network, and endpoint efficiency. John broadened his original Apple TV usage case to include Google Chrome Cast, Mobile Printing, File-Sharing, and other important services, thus improving the efficiency of trainees, teachers, and personnel.

    Given that 2019, the Cisco DNA Service for Bonjour has actually been extensively accepted and carried out solutions throughout a broad commercial domain, efficiently addressing relentless challenges. This advanced option empowers IT administrators to effortlessly incorporate their network community to accommodate revolutionary innovations, including contemporary computers and mobile device OS, audio-visual conferencing systems, the Internet of Things, and numerous other modern innovations in Business campus networks.

    Cisco DNA Service for Bonjour solution adoption Figure 4: Cisco DNA Service for Bonjour service adoption It is likely that your Enterprise network might still be running mDNS flooded under the hood, and if you have already invested in the above assistance matrix, then updating your network experience by following in the footsteps of John and over 7000+ other successful international Business clients could be a sensible choice. Cisco DNA Center will broaden a variety of release alternatives, from physical, and virtual to cloud-based. Talk to your Cisco sales team to identify the best alternative that meets your specific requirements.


    Cisco DNA Service for Bonjour– Solution Landing Page

    Cisco DNA Service for Bonjour– At-a-Glance

    Cisco DNA Service for Bonjour Implementation Guide

    Cisco DNA Service for Bonjour Deployment Guide– Conventional LAN and Wireless Resident Mode

    Cisco DNA Service for Bonjour Implementation Guide– Standard LAN and FlexConnect Wireless Local Mode

    Cisco DNA Service for Bonjour Implementation Guide– Cisco Software-Defined Gain Access To Mode

    Quick Configuration Guide

    Cisco DNA Service for Bonjour Quick Setup Guide

    Cisco DNA Service for Bonjour CCO Configuration Guide

    Cisco Catalyst 9300 Series Switches

    Cisco Driver 9400 Series Switches

    Cisco Driver 9500 Series Changes

    Cisco Catalyst 9600 Series Switches

    Cisco Nexus 9300 Series Changes

    Cisco Driver 9800 Series WLC

    Cisco Catalyst 9100 Series– Embedded Wireless LAN Controller

    Cisco DNA-Center– Wide Area Bonjour User Guide



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