Low speed and ARP timeout while multicasting



  • Hi folks, I tried multicast 5 machines this afternoon ( FOG 1.1.1 ) and it worked.
    They all get renamed and joined to the domain after imaging, that is really cool for me !
    but I have some issues :

    • When I download 1 image in unicast , the speed is around 1.5 Gb/min, but my 5 machines were less than 300 Mb/min in multicast ( as far as I’m a newbie ( and not a professional IT ! ) , I was thinking the multicast speed would not be divided by the number of machines …
    • More annoying, I’ve got a lot of PXE-11 error and ARP timeout with others machine on the network while booting.
      ( that disappear after the end of downloads )
      So I suspect a sort of overload of the server’s connections ?

    I’ve read some threads about these errors, understood the concept of " a chain is not stronger than the weaker link" and I have to check my switch’s configuration ( even if I don’t really know how to do that… ) and patches

    But maybe somenone has an idea

    PS : excuse my poor english, I’m french …


  • Developer

    [quote=“Flavalf, post: 30776, member: 24625”]Thank you Jaymes for your answer, I see there is plenty of messages claiming the team’s help on the forum and it’s not the best part of the job to answer and debug users … but it’s the price of fame.;)

    I have to say, my point was not to blame FOG, I never thought the cause was the program.
    You know, I’m just a teacher who is in charge ( with small time … ) of the network of my college ( nearly 400 Pcs ), and I just want with my poor knowledges to learn how it works and how it can works better !
    For sure, using FOG is already a great gain of time and headache for me and I thank you guys again.

    So, I will investigate my network as you told me and give feedback as i can.[/quote]

    I wasn’t trying to say you were claiming a bug per say, but then it could be! We change and break things often! So run some of these test on an isolated network and see if that helps to increase your imaging speeds. If not we can work from there!

    Thanks for being understanding, and good luck!



  • Thank you Jaymes for your answer, I see there is plenty of messages claiming the team’s help on the forum and it’s not the best part of the job to answer and debug users … but it’s the price of fame.;)

    [QUOTE] I understand you want to claim it is a bug and you want us to fix it. But do some work first, test on and off your network.[/QUOTE]
    I have to say, my point was not to blame FOG, I never thought the cause was the program.
    You know, I’m just a teacher who is in charge ( with small time … ) of the network of my college ( nearly 400 Pcs ), and I just want with my poor knowledges to learn how it works and how it can works better !
    For sure, using FOG is already a great gain of time and headache for me and I thank you guys again.

    So, I will investigate my network as you told me and give feedback as i can.


  • Developer

    Unicast sends image to clients, It decompresses at the server and sends to the clients, this is fast.

    Mulitcast checks in with clients and waits for each client to reach a check point to continue, this slows down imagaing, it also bombards your network.

    In mulitcast, because everything needs to be in the same checkpoint, decompresses the image at the server and then sends it to the requesting parties.

    I doubt it’s a problem at the server, but it could be. Read my first three comments, Read them again. Now read them again and understand it.

    [B]Multicast BOMBARDS your network[/B], this would cause a slowness, it’s just pushing out data. I would look at the switch gear between the FOG server and the hosts. For a real test, I would ISOLATE the FOG and my hosts and troubleshoot from there. I understand you want to claim it is a bug and you want us to fix it. But do some work first, test on and off your network.

    NONE of us that use FOG have an identical network setup. That being said, there may be something in your network that is causing the slowness, not FOG. Test off the network and compare to your notes. Try disabling settings in your switch and test.

    I would start with a “test” network and prod it until I was happy with it.

    PLEASE NOTE Later revisions of FOG have switched the process back to decompressing at the client side. I would download the latest revision and give it a go as well.


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