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Airplay Printers disappear

Posted on 2014-09-09
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Last Modified: 2014-09-26
Hello,

We have two HP Laserjet P1606dn printers on our 192.168.16.0/20 subnet.  They have Bonjour enabled.  We have users with Ipads/iphones on that same subnet.  When we first enable the Bonjour printers, the users can see and print to the printers.  But after a while, the printers disappear from the available printers list.  The only way to make them come back is to disable/enable the Bonjour service on the printers.  Its like a timeout happens and they disappear.

Other specs:
Switches are HP Procurves.
Gateway is a Sonicwall Firewall.  Multicast is enabled/allowed on the interface.
Wireless network is Aerohive with Bonjour Gateway enabled (although this doesn't come into play since the printers and users are on the same network).

Anyone have any ideas?

Thx.
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Question by:L8C
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21 Comments
 

Author Comment

by:L8C
ID: 40312221
Just to add, the printers used to work all the time.  The things that were changed were the VLAN on the switches, the subnet and the Firewall (Old one was a Juniper Netscreen).  

The issue might be IPv6 since the printers had that enabled and I know that the Sonicwalls don't support it yet.   I don't know enough with how Ipads, bonjour and IPv6 work.  

ANy help would be appreciated.  thx.
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Author Comment

by:L8C
ID: 40312878
So disabling IPv6 on the printers didn't help.
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Expert Comment

by:Craig Beck
ID: 40312930
Are the printers going to sleep?  I've seen lots of issues when devices go to sleep and don't restart services when the NIC comes back up.
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Author Comment

by:L8C
ID: 40313021
I don't think you can disable the sleep mode entirely from the web interface.  It only allows it up to one hour.  There's no "disable" or "never".
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Expert Comment

by:schaps
ID: 40313751
Check that IGMP is enabled on the Procurves on the VLAN in question - command: sh ip igmp config
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Expert Comment

by:Craig Beck
ID: 40313780
You don't specifically need IGMP for this - flooding will work anyway.  AirPlay is working though, just not after a client wakes.
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Expert Comment

by:schaps
ID: 40313821
AirPlay is working though, just not after a client wakes
The OP said that AirPrint-enabled printers disappear after a while, nothing about clients waking. Every Bonjour/AirPrint enabled printer I have seen continues to advertise even when in low-power mode, the NIC remains active. The clients in question are iOS devices, which also maintain a continuous network connection, even when in standby mode.
I think this is a problem with the network. I would normally suspect the AP's, but these are Aerohive, which are pretty Bonjour savvy.
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Author Comment

by:L8C
ID: 40314440
I thought about turning on IGMP on the vlan in question.  Didn't make sense that it would make it work but I didn't think it could hurt.  I'll try that and update.
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Expert Comment

by:schaps
ID: 40314514
I used to work in a HP Networking/Procurve school, and IGMP did improve mDNS/Bonjour function.
Something else to try is to download the "Discovery" iOS app, which lists available Bonjour services and see what it shows when the Airprint printers stop showing up vs. other services to perhaps find a pattern. Perhaps when a certain switch or access point is involved, for example, AirPrint discovery times out, etc. Perhaps if the iOS device is on an AP in the same network segment, the printer is visible, but not when in others, etc.
Finally, make sure the firmware is up to date on all the switches and printers. On the printers, there is a firmware update utility on the Self Test / Configuration page that updates the printer firmware version to the latest. It's a little more complicated on the switches, and it depends greatly on the switch models you have, but old firmware may have reliability issues with multicast.
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Author Comment

by:L8C
ID: 40314733
I did a packet capture on the firewall and it looks like the multicasts to 224.0.0.251 on UDP port 5353 stop after 5 minutes.  

WHen a IOS user wants to print, do they send a multicast out requesting services to return?

Or should the printer be constantly blasting out bonjour multicasts announcing his availability?

Thanks for all the help, btw.
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Expert Comment

by:schaps
ID: 40315411
The iOS device does not send out multicast/Bonjour anything requesting services, it only listens for service announcements on that IP and port. When you tap to print, it then starts the process of sending the print job. The printer doesn't constantly "blast" out bonjour multicasts, in the sense that the bandwidth used is negligible. If you enable IGMP on your switches, multicast takes even less bandwidth, because the switches only forward on multicast through ports which connect to clients who have joined a given multicast group.
HP has a pretty good summary of this at: http://www.hp.com/rnd/library/ethernet_switching/igmp.htm
There's no real downside to enabling IGMP on all your switches, as it just makes the whole process more efficient.
That's interesting about the packet capture you did -- does that mean you have multiple LAN interfaces on the Sonicwall?

Another interesting thing to try would be to wait until an iOS device no longer sees a printer, then put the iOS device into Airplane mode for a few seconds, then turn Airplane mode off. If the printer then shows up, that would suggest the problem is on the iOS device side of the equation. Also of interest would be to walk to different network segment areas to see if devices connected there see the printer after this apparent five minute timeout.

Be sure to check that printer firmware, I have seen a number of complaints about earlier AirPrint HP printers not working right, fixed by later firmware.
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Author Comment

by:L8C
ID: 40315575
Question is, if the IOS user doesn't send out a request multicast and the HP printer stops sending out HELLOs,   how do they find each other after this HELLO period ends?
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Expert Comment

by:schaps
ID: 40315598
Sorry I wasn't clear -- it's not really a hello period, Bonjour/mDNS works by continuous advertisement of the availability of the service and what current IP to find it. If you're sure that the packets you captured were from the printer, and they stopped, I might try capturing them at the local switch port it plugs into to make sure it's the printer that stops sending the Bonjour advertisements for AirPrint services. If you can verify that the printers stop sending after 5 minutes, then there is a definite bug in HP's firmware.

With IGMP enabled, one of the switches is elected a "querier" and polls devices to confirm the continued availability of services, but clients themselves do not send Bonjour messages, they just look for them.
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Author Comment

by:L8C
ID: 40315619
I will try that.  

BTW, i enabled IGMP on all the switches under the VLAN with "ip igmp".  It didn't seem to help.   I don't see any IGMP groups for 224.0.0.251 either.
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Expert Comment

by:Craig Beck
ID: 40316857
schaps is absolutely right in how it works.  However, I maintain that IGMP isn't a requirement at all no matter how much it may appear to help, so that isn't really where I believe you should be looking, and in any case, it works for a period initially.

Do you have other AirPrint printers which work without a problem, or any other Bonjour-based services which are ok?

As a test I would disconnect the Bonjour gateway from the VLAN temporarily to see if that has an effect.
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Accepted Solution

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schaps earned 500 total points
ID: 40317033
A common issue is wireless systems filtering out multicast packets, because in the wireless medium, multicast is essentially the same as broadcast, all devices receive/evaluate all packets going out from a given access point to its connected clients. I would not expect that is the case here, with a Bonjour-friendly system like Aerohive. Nonetheless, I recommended the free "Discovery" app to see what Bonjour services the iOS devices were seeing when this problem occurs, which would help rule out the iOS devices as the problem. I didn't hear back on that.

I didn't bring up the idea of packet capture/sniffing because it is beyond the typical troubleshooter here, but since you, L8C, do know how to do it, I think this issue would now best be troubleshot by sniffing back to the source, the printers themselves, by capturing the packets coming from the exact ports the printers connect to. If they cease sending out Bonjour AirPlay announcements after five minutes, that's the crux of the problem. If they do not cease, yet the Bonjour does not make it to the router, then you need to find out where the barrier is, and not knowing your network topology, there's no way we can guide you there.

You didn't respond whether the printer firmware is up to date, but I would absolutely confirm that before setting up more packet capture.
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Author Comment

by:L8C
ID: 40320087
Update:

We removed the printers from the subnet.  We then hooked up our PrintMeMobile server which basically proxies as any printer connected to it.  It sends out Bonjour multicasts on behalf of the printer.

Just to let you all know, the Bonjour service does NOT announce itself always.  The PrintMe Mobile server would only respond to queries sent by other hosts.  I did many wireshark captures to determine this.   Our issue now is that our wireless hosts are separated by a firewall and a L3 core switch from this Print Me Mobile server.   So now I just have to figure out how to forward multicasts from one HP routed vlan to another.   Anyone know how to do that?  I tried turning on PIM-dense and IGMP simultaneously on both interfaces but that didn't work.
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Expert Comment

by:schaps
ID: 40320133
I thought your Aerohive system has a Bonjour gateway?
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Expert Comment

by:schaps
ID: 40344545
In the initial post, you wrote, "Wireless network is Aerohive with Bonjour Gateway enabled (although this doesn't come into play since the printers and users are on the same network)."

But in the most recent post, you wrote, "We then hooked up our PrintMe Mobile server which ... sends out Bonjour multicasts on behalf of the printer… Our issue now is that our wireless hosts are separated by a firewall and a L3 core switch from this PrintMe Mobile server."

So you've changed how this is all set up, but you aren't using the technology which you already had (Bonjour Gateway), you put another server into the mix which is on a different network across a firewall. According to my research, you'd need the additional PrintMe Mobile Link software or PrintMe Mobile L100 appliance to get the multicast to the different subnets, OR you should be able to use the existing Bonjour Gateway in your Aerohive system (reference: pages 12-13 of PrintMe Mobile Installation Guide ).

Keep in mind that the service advertisements for AirPrint may be shared between subnets, but that doesn't do the actual printing, it just tells the hosts where the printers are. There must still be IP routing between the networks in order for the printers to get the data if only using the Bonjour Gateway.

Please update this case or close it.
Thanks
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Author Comment

by:L8C
ID: 40346776
Sorry for the delay in response.  

We actually had both Airprint printers AND the PrintMe Mobile server running simultaneously.  So we had both going on at the same time.  

In the end, I believe its a combination of things.  I think the printers were going to sleep after 30 minutes or so and thats why they disappeared.  Also the HP Procurve switches in between will never forward anything in the 224.x.x.x/24 subnet so we couldn't trick the HP's to forward Bonjour multicast packets (224.0.0.251) coming from the PrintMeMobile server.  No matter using IGMP, PIM-SPARSE or PIM-DENSE.

Aerohive does a good job from "repeating" the multicasts from the PrintMe Mobile server but the server will only respond to queries, he'll never announce himself unsolicited.   So unless somebody on the same subnet was requested Bonjour ipp printer service thru Bonjour, he was quiet and thus, Aerohive would time out the availability of Print Me mobile printers.

Confusing? yes!

But thanks again for all your help.  Giving you the points.
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Expert Comment

by:Craig Beck
ID: 40346980
So it was a sleep issue, not an IGMP or PIM issue.  Don't therefore understand how points were awarded as such?
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