Re: Bonjour Service (mDNS) for wired and wireless devices

Irfan-Ahmed · ‎03-06-2024

We have wireless and wired devices that uses Bonjour (mDNS) service to discover each other. I need to configure both wired and wireless devices in the same VLAN .

We have Cisco WLC 5520 and APs that support flexconnect feature. I need to configure APs and swithes so that all of them are in one broadcast domain.

One idea is to use flexconnect so that traffic is locally switches and devices can discover eachother .

I am not sure if SVI on switch will be gateway or WLC interface and how can we do VLAN mapping.

Any help will be greatly appreciated.

Rahul Kachalia · ‎04-24-2024

Hello,

The mDNS gateway processing on Cisco Catalyst Switch and WLCs will enable the service-routing to discover and distribute the services between VLANs on single device OR across IP/MPLS/VXLAN core networks.

Hence, you may not need to restructure IP subnet between Wired and Wireless networks with FlexConnect if mDNS is the key reason.

You may find the FlexConnect mDNS Deployment Guide below to build flood-free Unicast based mDNS service-routing in the network:

https://cisco.com/c/en/us/solutions/collateral/enterprise-networks/guide-c07-743788.pdf

thanks,

rahul.

Gaurav Kansal · ‎04-25-2024

Dear irfan,

If we talk about mDNS packet, it has only 1 TTL. So it can only reach to its first hop. If we consider wireless device both mDNS advertisement and query will only reach to its next hop which will be controller itself. Controller will act as mDNS gateway but it can only reply mDNS query to that client which is connected to controller. In your case you want to communicate mDNS between wired and wireless client so wired client newer receive mDNS query response from controller and vice versa.
You can try with flex connect, it looks technically it will work. In that case please check whom you have to configure mDNS gateway.
Also in your case using SVI will also not work because both device mDNS gateway will be different and as I mentioned they live only till next hop so both device will never know about each other through mDNS communication.

Please vote as helpful if you found my reply helpful.
GoodLuck..

Rahul Kachalia · ‎04-25-2024

Hello Gaurav,

Your feedback is correct when considering classic-way of handling mDNS applications using Flood-And-Learn technique. The older solution enabled on single centralized WLC as mDNS gateway operates in "Service-on-a-Stick" design supports service discovery between different bridge-domains. The network-wide flood-extension to single centralized WLC or any other gateway may support desired function, but as network expands multi-dimensionally the scale and performance becomes challenging on any products with central switching architecture. Further, it lacks taking into precise Wired network locations, Segmented user-group networks, i.e., VRF to limit service discovery within the context, prevent leaking that may impacts network security and much more.

With over an 6+ years, the Catalyst Switching and Wireless networking products have enabled fully-distributed mDNS processing that eliminated classic Flood-n-Learn to Service-Routing. As a result, the mDNS TTL=1 challenge you described does not exist. With end-to-end Unicast based mDNS service-routing, you may route the services based on IT defined selective services, limit discovery within proximity targets and control with advanced policies. The fully-distributed mDNS processing & Unicast based service-routing assists in enabling significant amount of mDNS service-instance scale, query processing and response, improve system and network performance and reduce the fault domain in larger campus as described in this mDNS - Still Flooding? blog.

I request you to review several content we have produced over the years and in every release to understand better mDNS service-routing solution and avoid flooding network with mDNS traffic as it may adversely impact network performance and security:

Solution Overview
Data sheet (https://www.cisco.com/c/en/us/solutions/collateral/enterprise-networks/datasheet-c78-740204.html)
At-A-Glance (https://www.cisco.com/c/dam/en/us/solutions/collateral/enterprise-networks/nb-06-dna-bonjour-aag-cte-en.pdf)
FAQ (https://www.cisco.com/c/dam/en/us/solutions/collateral/enterprise-networks/nb-06-dna-bonjour-faq-cte-en.pdf)

Solution Guides
Cisco DNA Service for Bonjour : Quick Configuration Guide (https://www.cisco.com/c/en/us/solutions/collateral/enterprise-networks/dna-service-bonjour-og.pdf)
Cisco DNA Service for Bonjour : SD-Access Wired and Wireless Deployment Guide (https://www.cisco.com/c/en/us/solutions/collateral/enterprise-networks/sd-access-wired-wireless-dg.html)
Cisco DNA Service for Bonjour : Traditional Wired and Wireless Local Mode Deployment Guide (https://www.cisco.com/c/en/us/solutions/collateral/enterprise-networks/dna-service-for-bonjour-dg.html)
Cisco DNA Service for Bonjour : Traditional Wired and Wireless FlexConnect Mode Deployment Guide (https://www.cisco.com/c/en/us/solutions/collateral/enterprise-networks/guide-c07-743788.html)

Success Stories
St. Vrain Valley School District (https://www.cisco.com/c/dam/en/us/solutions/collateral/enterprise-networks/nb-09-st-vrain-valley-case-study-en.pdf)

Videos
Cisco TechWise - Enterprise-Class Bonjour (https://www.youtube.com/watch?v=0NJfCXig7g8)
Cisco Catalyst TV – Traditional Wired and Wireless Networks (https://www.youtube.com/watch?v=qtRcb00Ue7E)
Tech Field Day – Cisco DNA Service for Bonjour (https://www.youtube.com/watch?v=10wJjPn1HBU)