[mpich-discuss] Loopback IPs should be filtered out by MPICH tools

[Jeff Hammond]

This may be related to https://trac.mpich.org/projects/mpich/ticket/1799
and  https://trac.mpich.org/projects/mpich/ticket/2213, or at least I
speculate that changing host hostnames are parsed might address all three
at once.

Jeff

On Fri, Aug 14, 2015 at 7:32 AM, Nevolin, Andrey <Andrey.Nevolin at emc.com>
wrote:

> Hi,
>
>
>
> I installed MPICH on a cluster deployed in a virtual environment. After
> that I spent a lot of time trying to figure out why it doesn’t work.
>
>
>
> I’m new to MPICH (and even to MPI). Hence my suggestions about the system
> functioning may contradict to the real world. But looks like in my case the
> problem has the following roots:
>
>
>
> 1) Looks like MPICH nodes use something similar to ‘hostname –i’ to
> discover their own IPs
>
> 2) If several IP aliases exist for a single host name, MPICH picks the
> first of them
>
> 3) Order of IP aliases resembles their order in ‘/etc/hosts/’ list
>
> 4) VMWare hypervisor automatically adds loop back alias for the host name
> (when the cluster is deployed by cloning of a single node). And this alias
> is added as a first line in ‘/etc/hosts’
>
> 5) All of the above means that MPICH discovers loop back IP in my case.
>
>
>
> The problem disappeared when I removed loop back alias from ‘/etc/hosts/’.
>
>
>
> Please, change IP discovery process to avoid loop back IP. Or add an
> explicit requirement to documentation to avoid loop back aliases in
> ‘/etc/hosts’.
>
>
>
> Thanks,
>
>                 --Andrey
>
>
>
> @Andrey_Nevolin <https://twitter.com/Andrey_Nevolin>
>
>
>
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-- 
Jeff Hammond
jeff.science at gmail.com
http://jeffhammond.github.io/
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