Are you having an issue setting up AirPrint, AirPlay or perhaps ChromeCast on your Aruba Instant AP network? I did. It turns out to be a super easy fix, especially for home user’s perspective.
Situation
I can’t find printer(s) via AirPrint on my Aruba Instant WiFi Network.
- Similar issues maybe I can’t cast my screen/music via Airplay or ChromeCast on my Aruba Instant WiFi Network
Background
AirPrint, AirPlay, ChromeCast fall under the type of technology called zero-configuration networking. Bonjour is one such standard developed by Apple and used for specific services like AirPrint.
From the layman’s perspective, these technologies allow end user experience of us seeing devices like a printer on the same network without us knowing the device’s specific IP address.
Under the hood, these technology needs to probe network by sending non-targeted data. This is fine in a home or perhaps small office setting.
As such frequency, number of devices to probe are fairly limited. However, if this was in an enterprise setting such as at a University or big cooperation, these probing traffic can become a serious network congestion source, and results in actual performance degradation (ref). So in an enterprise setting, multicasting/broadcasting are not recommended in general. So Aruba has decided to turn this feature off by default.
Assessment
Aruba has multicast/broadcast that allow zero configuration network setting like AirPrint turned off by default.
Recommendation
Turn on multicast/broadcast service.
Disable Broadcast filtering
Configuration > Networks > SSID Edit > Basic | Show advanced options > Broadcast filtering = Disabled
Once you make this change, make sure to follow through the rest of SSID configuration and hit finish to save the change.
At this point, you should be able to see AirPrint printers, Airplay etc. so long as you are on the same VLAN as the printers.
Technical Deep Dive
In this section, we are going to take a close look at under the hood technology. This section is only for those who cares about what we are doing. As a casual network hobbyist, I like to learn these details and believe understanding the technical basics will help for troubleshooting.
According to the of official Aruba Instant 8.11.2.0 User Manual, the default setting of broadcast filter ARP means Instant AP drops all broadcast and multicast frames except DHCP and ARP, IGMP group queries and IPv6 neighbor discovery protocols. Since zero configuration protocols such as Bonjour does not fall under these exceptions, it is indeed blocked by default. So it makes sense to disable the filter.
Just below the Broadcast filtering, there are two related options.
- Multicast transmission optimization
- Dynamic multicast optimization
According to the official user guide, my understanding of two options are as follows:
- Multicast transmission optimization will send multicast data at the fastest possible rate, which is basically the slowest associated client’s speed.
- Dynamic multicast optimization will convert multicast streams into targeted unicast stream over the WiFi.
Both should improve multicast data transmission and overall reduce network congestion. I think it’s perfectly reasonable to turn these options on and see if you notice any improvement in your system performance. Specifically, the dynamic multicast optimization is said to improve quality and reliability of streaming video. So if this is something you are looking for, try and see what happens.
Personally, I like to keep relatively standard, default setting unless there is a good reason to make a change. This is simply as a non-pro network user, I have encountered enough situations when changing certain things just because they sound good, resulted in creating unexpected issues later down the road, and those make much harder to trouble. So my motto is, keep it simple, do no harm.
One tip is if you are making any change to the default setting, it is a good practice to keep track of what you have changed and when, so later if you want to troubleshoot, you know exactly what you have touched in the past.
AirGroup
Another broad cast related feature in Aruba is AirGroup. Tis feature allows selective broad casting and multi-casting, and I believe it’s a needed setup on large scale, enterprise setting to ensure broadcast do not become the major source of network traffic.
Reference
- Aruba Instant 8.11.2.0 User Manual
- Configuring WLAN Settings for an SSID Profile Table 15