Hyper-V 2012 R2.u1 Gen1 VM vs the Kernel



  • This article is the result of this previous thread.

    I think I’ve figured it out.

    When kernel 3.18.5 and earlier versions enumerate the interfaces in a 2012 R2.u1 Hyper-V Generation-1 Virtual Machine, it only has drivers to recognize the Legacy adapter (eth0). it ignores whether you have the ‘Ethernet’ adapter (eth1) connected to the virtual switch or not.

    Kernel 3.18.5 then uses the 100Mb Legacy adapter (eth0) that it PXE booted from to transfer to/from the FOG server.

    Beginning with my use of kernels 3.19.1 on up to the current version 4.1.4 kernel, I’m guessing that the driver for the Hyper-V ‘Ethernet’ adapter (eth1) is included. If the ‘Ethernet’ adapter (eth1) is disconnected, like I had been doing for kernels 3.18.5 and older, 4.1.4 will not fail back to use the ‘Legacy’ adapter (eth0), but will fail the process in an infinite spit out of CR+LF, or error out with network interface (eth1) not found.

    If when using kernels 3.19.1 on up, the ‘Ethernet’ adapter (eth1) IS connected to the virtual switch at the same time as the Legacy adapter (eth0), the VM will PXE boot from the Legacy adapter (eth0), then uses the 'Ethernet" adapter (eth1) for the data transfer.

    … and there was much rejoicing.

    As a bonus, using the ‘Ethernet’ adapter (eth1) for the data transfer means using a 1Gb connection; ergo, roughly 1/8 the time required for data transfer.


  • Moderator

    @sudburr said:

    What didn’t make sense?

    I was rushing, it makes more sense now. Today was really hectic, apologies.



  • Yes it is fixed. I set the message threads to solved.

    What didn’t make sense?

    Many, many thanks for all of your patience and assistance with this unusual problem that took so long to percolate until I had my eureka moment.


  • Moderator

    So is this fixed for sure in the current kernel or was it a site-specific thing?

    I did read everything you posted, but I can’t say it made a lot of sense and I didn’t spend much time on it…

    I just need to know what to tell other people having the issue.


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