netdev - Re: how to (cross)connect two (physical) eth ports for ping test?

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Message-ID: <alpine.LFD.2.21.1808190429230.8071@localhost.localdomain>
Date:   Sun, 19 Aug 2018 04:29:47 -0400 (EDT)
From:   "Robert P. J. Day" <rpjday@...shcourse.ca>
To:     Willy Tarreau <w@....eu>
cc:     Andrew Lunn <andrew@...n.ch>,
        Linux kernel netdev mailing list <netdev@...r.kernel.org>
Subject: Re: how to (cross)connect two (physical) eth ports for ping test?

On Sat, 18 Aug 2018, Willy Tarreau wrote:

> On Sat, Aug 18, 2018 at 09:10:25PM +0200, Andrew Lunn wrote:
> > On Sat, Aug 18, 2018 at 01:39:50PM -0400, Robert P. J. Day wrote:
> > >
> > >   (i'm sure this has been explained many times before, so a link
> > > covering this will almost certainly do just fine.)
> > >
> > >   i want to loop one physical ethernet port into another, and just
> > > ping the daylights from one to the other for stress testing. my fedora
> > > laptop doesn't actually have two unused ethernet ports, so i just want
> > > to emulate this by slapping a couple startech USB/net adapters into
> > > two empty USB ports, setting this up, then doing it all over again
> > > monday morning on the actual target system, which does have multiple
> > > ethernet ports.
> > >
> > >   so if someone can point me to the recipe, that would be great and
> > > you can stop reading.
> > >
> > >   as far as my tentative solution goes, i assume i need to put at
> > > least one of the physical ports in a network namespace via "ip netns",
> > > then ping from the netns to the root namespace. or, going one step
> > > further, perhaps putting both interfaces into two new namespaces, and
> > > setting up forwarding.
> >
> > Namespaces is a good solution. Something like this should work:
> >
> > ip netns add namespace1
> > ip netns add namespace2
> >
> > ip link set eth1 netns namespace1
> > ip link set eth2 netns namespace2
> >
> > ip netns exec namespace1 \
> >         ip addr add 10.42.42.42/24 dev eth1
> >
> > ip netns exec namespace1 \
> >         ip link set eth1 up
> >
> > ip netns exec namespace2 \
> >         ip addr add 10.42.42.24/24 dev eth2
> >
> > ip netns exec namespace2 \
> >         ip link set eth2 up
> >
> > ip netns exec namespace1 \
> >         ping 10.42.42.24
> >
> > You might also want to consider iperf3 for stress testing, depending
> > on the sort of stress you need.
>
> FWIW I have a setup somewhere involving ip rule + ip route which
> achieves the same without involving namespaces. It's a bit hackish
> but sometimes convenient. I can dig if someone is interested.

  sure, i'm interested ... always educational to see different
solutions.

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                  http://crashcourse.ca/dokuwiki

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================