Networking problems – how to troubleshoot?

Discussion in 'Mac OS X Server, Xserve, and Networking' started by mabam, Apr 19, 2017 at 2:12 AM.

  1. mabam macrumors newbie

    Sep 20, 2015
    Ever since I upgraded to Mountain Lion a few years ago (yes, I am still running it for the sake of some old software) I have network problems. They might be related to Parallels Desktop 8, as always when I had started a VM I couldn't reach my NAS via AFP from the host machine until I had restarted the computer.

    Also, Parallels interfered with a networked version of SheepShaver. But I don't remember the details about that.

    I have a new NAS now serving as print server as well. After setting up the NAS I could click on it in the sidebar of any finder window in OS X (again via AFP), and then access any volume on it. I could print to the printer it shared via CUPS. Now, I have to connect to it via cmd-K and enter afp://IP_ADRESS there. And I cannot print anymore as OS X can't find the printer (it sometimes can via the "add printer" window in system preferences, but never when I want to actually print). The connection between the NAS and the printer is fine, however.
    I can't imagine the problem is with the NAS. I just set up its system from scratch yesterday but am not back to how I could access it for a short period after I initially set it up a few months ago.

    Can anyone help in finding out what is wrong?
  2. organicCPU macrumors regular


    Aug 8, 2016
    What exactly is 'Now'? Do you mean after attaching/installing the new NAS? Is the old NAS still available for making comparisons? Configuring advice for the NAS is easier to give by someone that knows what NAS it is: Qnap, Synology, etc. Some people seem to have similar issues here and here.

    My five cents:

    - AFP is depreciated in favor of SMB. If the NAS OS Version is a more recent one, proper functional AFP is most likely not considered as very important by the dev team. Watch for updates of the NAS OS or make a bug report to the developer.

    - Is the printing service configured and up and running on the NAS? Can CUPS access the spool folder on the NAS -> folder or user privileges
    - Try to turn off the NAS firewall and see if printing is working. Don't forget to turn it on again. -> Printing Port configuration
    - Try to turn off your Mac's firewall and see if some incoming service is blocked. Don't forget to turn it on again. -> Application firewall configured to block daemon.

    - Find the login key in Keychain Access where your afp login credentials are stored, delete it, reboot or logout and create a new one by simple reconnect to the NAS like you used to -> shared keys are outdated

    - The Parallels networking problem could be some bug with the virtual network adapter created by Parallels. That seems to be a different problem to solve as you said it persisted before the new NAS. As I don't have Parallels, I have no idea. With VirtualBox on 10.8. ML I have no network problems. As a starting point Wireshark and/or the Terminal commands ping, netstat, ipconfig, networksetup are your friend to get more insight what happens before and after running Parallels.

    - I guess SheepShaver is creating some more virtual network instance that could interfere if misconfigured or buggy. Then there is some very old Classic OS running in there that has a totally different version of network protocol running. There is a great website that deals with Mac OS Classic network setups that could help.
  3. mabam, Apr 20, 2017 at 5:27 AM
    Last edited: Apr 20, 2017 at 6:23 AM

    mabam thread starter macrumors newbie

    Sep 20, 2015
    'Now' means since a few weeks, while the new NAS is running since the end of last year. Initially it did work and while I didn't change anything, at first I only had the problem that the NAS disappeared from the sidebar after I had used Parallels, and it was working fine again after a restart. Then this problem began to arise more and more, even without using Parallels, and eventually restarting the machine wouldn't resolve it anymore. So far, everything was AFP related. But since maybe this month I can't print anymore, which shouldn't be AFP related as OS X doesn't connect to a CUPS server via AFP, afaik.

    The old NAS was a Synology DS-106j and simply wouldn't work anymore some day (which was no wonder after the years it was running). I wanted the new one to be capable not only of AppleTalk via IP (which the DS-106j had provided as well), but also via DDP. It is therefore self-built (into the housing of the broken DS-106j) around a Banana Pi hardware-wise and an A2SERVER installation software-wise. That way it can serve as fileserver for basically any Mac ever produced, and as printserver for my good old LaserWriter 4/600 PS only speaking PAP via LocalTalk. I just finished the detailed setup guide this week:

    A2SERVER is a package made for running on present versions of Ubuntu or Debian, while providing AppleTalk/AFP from an Apple II up to present OS X systems, using a fixed version of netatalk and other software.
    Printing from OS X via the A2SERVER system (Banana Pi) worked fine until it simply wouldn't anymore some day without any known reason.

    When I assign a PPD to the printer on the server side, blank pages get printed. So I set it up as raw printer and assigned the PPD on the client side (OS X). At I have described in detail how I set up CUPS. As written above, that used to work fine. I didn't change anything in the CUPS settings since. But I'm definitely not a expert, so maybe there's something wrong or missing in my setup guide.

    There's no firewall to turn off at the NAS, as it doesn't have one. The Mac can't find the printer, even with the firewall turned off in OS X.

    I use Parallels as it works very well for a VM with Snow Leopard Server (I need Rosetta). I also like the coherence mode. I'm still on Parallels 8 for that, as Snow Leopard support got worse in v. 10.
    It's not so much about networking problems in the VM's of Parallels. With both, the old and the new NAS, their respective volumes would disappear from the sidebar in an OS X window on the host system when I'd start a VM in Parallels. Same thing with Parallels 10 when I had it running for testing.

    There's no login key for AFP in Keychain Access. Probably because I access the AFP volumes without any password, just as guest.

    I barely ever use SheepShaver. It gets connected to the network by a bash script that is executed prior to starting SheepShaver. It uses a tap device and a bridge in order to bypass OS X. That way SheepShaver can speak AppleTalk via DDP. The only thing left when SheepShaver does not run is the fact that TunTap is installed, but not used at that moment.

    Thanks for your tips and suggestions so far. I'll try Wireshark and the Terminal commands. But it might take some time as in a few days I'll leave the country for a week.

    One thing I forgot to mention: After I had set up the NAS last year, next to clicking on it in the sidebar, I could connect to it via afp://bananapi when using cmnd-K. Also, I could SSH into it with "ssh $USER@bananapi". At some point the name could not be resolved anymore and I had to use the Banana Pi's IP address for both, via cmnd-K and SSH.
  4. mabam, Apr 20, 2017 at 10:19 AM
    Last edited: Apr 20, 2017 at 11:33 AM

    mabam thread starter macrumors newbie

    Sep 20, 2015
  5. mabam, Apr 20, 2017 at 11:31 AM
    Last edited: Apr 20, 2017 at 12:01 PM

    mabam thread starter macrumors newbie

    Sep 20, 2015
    OK, I clearly have a name resolution problem on the OS X machine.
    I clicked on the printer in the CUPS browser interface of the Banana Pi and copied the URL (incl. 'http'). Then I went to the CUPS browser interface of the OS X machine, added a new printer as "Internet Printing Protocal (IPP) (http)" and pasted the copied URL as printer address. Now I can print again without issues.

    It seems to be an issue with Bonjour. That is what OS X uses to automatically recognize network printers and AFP servers. Since months, the Remote app on my iPhone can't find iTunes anymore either. This seems to depend on Bonjour as well after what I read about it.
  6. organicCPU, Apr 20, 2017 at 7:52 PM
    Last edited: Apr 20, 2017 at 9:53 PM

    organicCPU macrumors regular


    Aug 8, 2016
    You've got an interesting setup running. That you could manage to print is very good to hear.

    To be honest, I have no better idea than somehow fighting the probably existing name resolution problems. If you can connect through the IP address, making aliases of the TCP/IP connection and dropping them to the sidebar could be an interim solution.

    It's a little strange that things went worse over time without a clear reason. A broken cable can get worse or a switch or even a network card can make some slow fade away if capacitors are bursting one after one. That some services disappear over time is really weird.

    If I understood you right, there are just two machines in your network. A Mac running 10.8.x with a Parallels VM 10.6.x Server and a SheepShaver instance with TunTap as the first machine and as the second machine a Banana Pi NAS running Debian and an A2SERVER on top plus a LaserWriter attached. That means that you can't compare if it works on another Mac.

    You could try creating an additional fresh test account on the Mac without the VM and Emulation to see if e.g. a broken plist file can be the reason of all this or if TUN of TunTap is routing to nowhere. If it's a Bonjour thing on the Mac side problems should disappear with a fresh account. Playing around with IP v6 settings could be worth trying (local-link).
    To exclude any possible software failure on the Mac, you could go this far to make a fresh install of Mountain Lion on an external USB drive and boot from there. If that doesn't solve the issues or at least some of them, I'd dig more into the Banana Pi.

    If I remember correctly, my PPC / Mac OS 8.6 doesn't like some username/password combination that was too long or had special chars in it. As you log in as a guest, that shouldn't matter. Nevertheless I guess a too long or exotic device name (mDNS) can be problematic, too.
    Concerning the DDP setup, the Name Binding Protocol (NBP) seems to me like the counterpart of Bonjour and as you wrote the Printer Access Protocol (PAP) should be responsible for printing. How to configure them is beyond my scope. These Mac OS 7 and 8 days I was a newbie and never dealt with those settings. I didn't have a special Apple Talk Zones setup and was just using the Asterisk (*) as Apple Talk Zone.

    Here is another link for setting-up networks that could be of interest. Apple has a Bonjour Community for Windows that could give at least some inspiration as well. Maybe the Bonjour Browser can help with debugging, too. Good luck to track down the problems. Would be interesting to hear from your progress.

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