Apple iPads, Apple TVs, Bonjour & AirPlay Across Subnets Using Open-Source Software
As more schools implement wireless networks, BYOD programs, and Apple TVs, they are quickly finding that on properly configured and subnetted networks they are unable to locate their wired Apple TVs with their wireless iPads, iPhones, Andriod devices, etc and therefore are unable to use Apple's "AirPlay" to stream music or videos to their Apple TVs, and are also unable to mirror their iPad's screen to the Apple TVs.
This is because the protocol by which Apple devices announce themselves and locate other Apple devices on a network does not work when these devices are on different subnets.
AppleTVs and other Apple devices on home networks don't have any problem locating each other. All the devices appear to magically "just work"(TM) together because all the devices are on the same subnet (broadcast domain) and Bonjour works perfectly fine in this type of small, non-routed network.
However, Bonjour is a multicast (broadcast) protocol, and as such does not traverse across routers to other subnets. When Apple devices are on a larger, properly segmented (subnetted) network, Apple devices on one subnet will not be able to locate Apple devices on another subnet.
To solve this issue, several companies (including Aerohive and Aruba) have created what are referred to as "Bonjour Gateways." When installed on a network, these gateways listen for mDNS traffic on all subnets they that are directly conected to and then re-broadcast the mDNS traffic onto all the other subnets they are directly connected to. This allows Apple Bonjour announcements on one subnet to be heard by devices on the other subnets.
We have found that these commercial solutions don't always work as expected, and they are either not free, not open-source, or they require that you purchase the vendor's wireless hardware - locking you into one company's wireless system.
Another concern that we have with these implementations (such as the Aerohive Bonjour Gateway) is that they are cloud-based, and actually require that you and your "Bonjour Gateway" connect to Aerohive's "Hive Manager" to manage and configure your devices. This allows for the possibility that Aerohive can collect information about your internal, private network, its configurations, and possibly even the traffic on it. We consider this to be a security risk and something that network administrators need to be aware of before jumping into this type of a cloud-based solution.
Every major distribution of the free, open-source Linux operating system comes with a program called "Avahi." Avahi is the free, open-source implementation of the mDNS protocol. With a few changes to the Avahi configuration file, you instantly have a free, open-source "Bonjour Gateway" that does not need to talk to any "Hive", nor any other external entity to function properly. The private information about your network and your network traffic STAYS IN YOUR CONTROL!
At our clients' sites where wired AppleTVs are connected to different subnets than their wireless devices, we install and configure a virtual Linux server running the Avahi service. With this server in place, our client's wireless iPad users are able to quickly locate their wired AppleTVs and stream music and videos, or mirror their iPad's screen to any available AppleTVs regardless of the subnets they are on.
Already have a virtual server infrastructure such as VMware's vShpere in place? Ask us for a demonstration of an open-source Bonjour Gateway!
See It For Yourself
Don't have a virtual server infrastructure in place yet? Click HERE to learn how virtualizing your server infrastructure can help save you time and money, and then ask us for a demonstration of an open-source Bonjour Gateway!
Detailed instructions and Diagrams!
This is just a short, basic, informational post. I am working on detailed instructions complete with screenshots and diagrams which I hope to post in the coming weeks.
10/01/13 UPDATE: Part two of this post has been added. Click HERE to view it.