Pi-Hole and AirPrint services

Wetty · February 11, 2020, 10:10pm

Hello, has anyone experienced their in-house ( behind the Pi-Hole - internal house network) lose functionality after a Pi-Hole install?
I have a Pi v4 and Raspbian sitting behind my ISP router and working wonderfully for internal devices on my LAN/WiFi networks. Its amazing how effective these can be, how much they block and the speed increase once search and DNS start working for you.
I have a big collection of devices across a range of OS: Windows, iOS, versions of Linux in IoT Devices, Ring, etc. My Pi-Hole is now functioning as a complete DNS and DHCP Server. I have disabled IPv6. Before the Pi-Hole was running, my HP6978 Inkjet printer printed AirPrint jobs perfectly. Since the install I have not been able to see the printer over AirPrint. I have tried adding MAC and IP reservations, and I have confirmed the printer does have AirPrint enabled from its Admin pages. I have restored WiFi printing from my Windows devices, however the AirPrint is not functioning.

Has anyone come across this, and have any tips for troubleshooting AirPrint on a Pi-Hole supported network?

RamSet · February 11, 2020, 10:52pm

Hello and welcome !

I don't think Pi-hole has anything to do with the service itself as Pi-hole is only a DNS resolver and does not interfere with bonjour.

Use the following guide to troubleshoot:
https://www.printsupportcenter.com/hc/en-us/articles/115004181705-AirPrint-No-printers-visible-on-Apple-iOS-devices

Also check the printer's web gui for any errors/additional information about AirPrint.

The only thing I can think of is a stuck/old AirPrint setting on the printer that broadcasts (or NOT to be more exact) wrong info.

See if you can reset the printer to factory settings with Pi-hole active, in order for it to self configure with the fresh network environment.

Bucking_Horn · February 12, 2020, 10:26am

mDNS, implemented e.g. by Apple's Bonjour or Unix's avahi, as a decentralised, auto-configured protocol for resolving local network hostnames, normally quite happily coexists with DNS

I am aware of only one potential issue here:
mDNS uses .local as its default domain name.

You might want to verify that your network does not use this very domain name as well (e.g. if you'd configured that name when using Pi-hole as your DHCP).

Wetty · February 12, 2020, 8:27pm

Than you. I looked at this and it doesn't appear free. Am I missing something? Is there a version for Pi that is no cost?

Wetty · February 12, 2020, 8:28pm

Thanks, I looked at this, I have my own local ( in house domain not labelled this) so no issue there. I looked into mDNS but I only see MacOS and iOS versions, is this something that needs to run on the Pi?

Wetty · February 12, 2020, 8:33pm

Ah ok, I grabbed the Bonjour Browser for Windows from Hobbyist Software, and I am not seeing Bonjour broadcasting, so my theory is correct that the AirPrint service isnt being seen. So, this needs to be enabled on the Pi-Hole, I believe. Anyone worked on that? I get the Pi-Hole is merely providing DNS resolution assistance and ad blocking, but acting as a DNS/DHCP Server it need to enable this service to pass through, broadcast etc. I am little limited in the term to use, but this worked on my home ASUS router before with no additional tweaks, as well as on the original Comcast XFinity router, so the difference now appears to be happening at the Pi-Hole DNS/DHCP level......

Bucking_Horn · February 12, 2020, 8:51pm

No, you misunderstand mDNS - have a read at the link I provided above.

mDNS does not require a dedicated server, nor does it require every client on the network to understand mDNS to operate correctly.

In layman's words, your printer will broadcast its name and its services to the network it is connected to. Each mDNS client will then pick up this information and update its local mDNS list accordingly. Likewise, your Apple devices will broadcast their names each, so any mDNS client will be known by name.

Pi-hole's DNS is not involved in any of this.

You may have a point about DHCP.
Your printer may not be able to solicit an IP address via DHCP from Pi-hole.
That could happen if your Pi-hole and your printer are located on different network segments with no DHPC relay agent between them.
However, I would expect an error message on your printer in that case, and your printer's MAC would not show on Pi-hole's DHCP panel.

From what you wrote, it seems unlikely this is the case, but better check.

I also recall a recent other post complaining about a network printer~~, but I think it was in German~~. I'll post again if it's relevant here.

EDIT:
It isn't in German, and it doesn't mention AirPrint, so it may not be related.
I link it nevertheless: The OP of Network Printer Issue with Pihole - #20 by englischdude was able to resolve the issue by disabling IPv6, updating the printer's firmware and powering down printer, Pi-hole and router.

Wetty · February 13, 2020, 5:30pm

Thanks - I believe I have a networking issue that has been caused by the Pi-Hole being introduced. I apologize for the basic questions, but I am not a networking expert. I have attached a home network diagram, and I had the following questions:

Do I need to have static routes configured anywhere in order for the Pi-Hole DNS to manage full network service broadcast such as Bonjour and most importantly AirPrint
Do I need to address anything in the firewall of the Pi-Hole device in order to unblock #1 .
I know UDP5353 is a Post Airprint relies on being available, but I am not sure where this must be enabled.
Does the Pi-Hole need any form of Static assignments for the above to operate? The gateway, Pi, DNS all have statics
All web outside of wireless printing is working perfectly ( and faster!) so this is the only thing causing an issue
Airprint worked before the Pi-Hole was introduced to the network

Any help would really be appreciated.

Wetty · February 13, 2020, 5:32pm

Quick point of clarification - the printer is receiving an IP from the Pi-Hole DHCP no problem at all, just like every other device. In addition, in the DNS/DHCP Pi-Hole Admin console I see the Printer registering properly. Same network segment as all other devices.

Bucking_Horn · February 13, 2020, 8:07pm

Absolutely no need to - lending support or patching up knowlegde gaps is among the most preeminent reasons for this forum to exist.

So let me repeat:
mDNS does not require a dedicated server. In fact, mDNS has been incepted to perform DNS-like operations on the local network in the absence of any DNS server, and it's been designed to require zero configuration.

Pi-hole as DNS server *cannot* in any way obstruct mDNS operation (EDIT: click for more).

This also means the answer to your questions 1., 2. and 4. is: No.

And just to put things straight for your 3.:
AirPrint uses port 631 (IPP) to submit print jobs, while device discovery is done via mDNS (using port 5353).
Again, Pi-hole does not interfere here, as it is not concerned with routing at all.

So your problem is most likely not a Pi-hole issue, even though I do not discard that it may have been provoked by introducing Pi-hole into your network.

Now, my next assumption may be a bit of a far call, but I think your network diagram (thank you!) contains a hint to a possible mismatch:

Looking up the specs, it seems your HP 6978 is equipped with built-in WiFi 802.11b/g/n, which means it operates solely on the 2.4GHz band.

Your router, on the other hand, is capable of providing 2.4GHz as well as 5 GHz WiFi. Even if your router is advertising them with the same SSID, this may constitute two separate network segments.

As far as mDNS multicast messages are concerned, this means they would only be visible for devices sharing the same band.

The quickest way to check this would be to disconnect all your WiFi devices, then disable your 5GHz network on your router and reconnect them, effectively forcing all of them to use the 2.4GHz band.

system · March 5, 2020, 8:07pm

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