[j-nsp] vMX questions - vCPU math

Nikos Leontsinis nikosietf at gmail.com
Tue Jan 1 12:59:38 EST 2019

For the Junos upgrade you will have to follow the same steps as you
did when you first installed the vMX. which effectively means no issu
and no traditional request software add... etc. You are looking for a
downtime for sure (extended or not depending on the engineer's skills)

Following are the getting started guides that has detailed steps on
how to install a vMX.

vMX Getting Started Guide for VMware :


vMX Getting Started Guide for KVM :


With regards to the questions about performance Juniper will give you
some guidelines but they are no binding in any sense this is a
uncharted territory for
all of us and everything depends on the use case and the traffic load.
If something happens (you are on your own) no service contract will
cover you Juniper
will blame the hypervisor vendor and the other way round. Don't put
anything into production if you don't test it thoroughly and don't
trust anyone else but what you see in the lab.

Also something else you need to know and observe is that the vswitch
has no state which effectively means you need to enable bfd on your
interfaces if you want to have some decent convergence.

On Sun, 30 Dec 2018 at 08:54, Robert Hass <robhass at gmail.com> wrote:
> Hi
> I have few questions regarding vMX deployed on platform:
> - KVM+Ubuntu as Host/Hypervisor
> - server with 2 CPUs, 8 core each, HT enabled
> - DualPort (2x10G) Intel X520 NIC (SR-IOV mode)
> - DualPort Intel i350 NIC
> - vMX performance-mode (SR-IOV only)
> - 64GB RAM (4GB Ubuntu, 8GB vCP, 52GB vFPC)
> - JunOS 18.2R1-S1.5 (but I can upgrade to 18.3 or even 18.4)
> 1) vMX is using CPU-pinning technique. Can vMX use two CPUs for vFPC ?
>    Eg. machine with two CPUs, 6 cores each. Total 12 cores. Will vMX
>    use secondary CPU for packet processing ?
> 2) Performance mode for VFP requires cores=(4*number-of-ports)+3.
>    So in my case (2x10GE SR-IOV) it's (4*2)+3=11. Will vMX count the
>    cores resulting from HT (not physical) in that case?
> 3) How JunOS Upgrade process looks like on vMX ? Is it regular
>    request system software add ...
> Rob
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Nikos Leontsinis
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Twickenham, TW1 2PF
GSM: +447809583514
skype: leontsinis2

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