Netbooting issue with Netgear switches

Discussion in 'Mac OS X Server, Xserve, and Networking' started by LSDWho, Mar 2, 2015.

  1. LSDWho macrumors newbie

    Aug 27, 2014

    We’ve started having issues with Netbooting since we recently replaced our network hardware, going from very old (10 yrs +) 3Com switches running at 100MB to desktop / 1GB backbone to brand new Netgear switches at 1GB desktop / 10GB backbone.

    On the old network hardware Netbooting would work fine, showing a list of Netboot images that we are able to boot from with no issue (mainly used for DeployStudio). We have two Mac servers on our network, and now, rather than being able to get a list of Netboot images, it seemingly selects one of the two “Default” images (one for each server) at random. Whichever image is selected works correctly, but we now have no way of choosing at time of bootup.

    Other than replacing the switches, nothing else has changed (that I am aware of) that could have caused this to stop working. However, some relevant info:

    • The new Netgear switches are generally M5300-52G-POE+ with a small number of XSM7224S.
    • Spanning Tree is enabled on the switches (set to Rapid Spanning Tree – 802.1w). Have also tried with STP turned off totally as I understand this may make a difference – however it did not.

    • The infrastructure is a mixed network, with both Windows PC’s/Servers sitting on the same network as the Macs. DHCP is supplied by one of the Windows servers.

    • No VLAN’s are set up – all running on same network.

    • Both Mac servers are sitting in different physical locations on the network. One is running 10.9.4 and the other on 10.6.8

    • If I boot holding down Option then I only see the local hard disk.

    • If I boot holding down either N or Option N then the Mac boots using one of the two Default Netboot images, seemingly at random, from one of the two Mac servers. This is as expected for Option N, but N alone used to bring up a list of images (including those not selected as the default on either server).

    • All the netboot images show up correctly within the Startup Disk option within System Preferences. I can then boot successfully from any of them in this manner, and am therefore able to get round my problem in the short term, but of course this isn’t ideal.

    • I have tried setting the netinstall images to be available both over HTTP and NFS, but this has no effect. Also there are no access restrictions in place for any of the images.

    I’m not 100% convinced that the issue is related to swapping to Netgear switches. Particularly as no specific configuration was ever done on the old 3Com switches to get netboot working (it just worked from the start). Also, the new switches are so much quicker than the old ones. That said it seems far too coincidental that this started happening when the switches were swapped over, and that as I said before, nothing else has changed.

    If there’s anything anyone can suggest that I can check, both with the switch configuration or otherwise, I’d be really grateful.

    Finally, just to say I’m more a Windows person than a Mac man, so treat me gently 


  2. Soverc macrumors member

    Oct 7, 2005
    Please post resolution when found

    Please post resolution when you find it, I am very curious as to the solution ,I have no idea and interesting puzzle.

    Things to try and get more info to narrow issue

    If you still have the old 3com switch put that in between client and server and test. If desired behavior you know it has something to do with new switch or if not you know the new switch is most likely not the culprit.

    Try setting the port connecting to one of the client machines to be the same speed and duplex as the old 3com ports were. If that works compare a sniffer or wire-shark tcp dump between new speeds and old speeds.

    QOS ? is this enabled it do turn off

    Good luck, this sounds like it is going to take 5 more mins or 5 more days and they are the worst type of issues.
  3. LSDWho thread starter macrumors newbie

    Aug 27, 2014
    Alas I no longer have the 3Com switches - they were all disposed of when replaced with the Netgears.

    Someone has pointed me in the directed me in the direction of DHCP relaying as this apparently can have some impact on Netbooting.

    I'm going to try a couple of things relating to that and will update one way or the other.


  4. Consultant macrumors G5


    Jun 27, 2007
  5. LSDWho thread starter macrumors newbie

    Aug 27, 2014
    We're not using jumbo frames no. Frame size set to 1518 bytes

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