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Re: [lvs-users] Real server not responding back

To: "LinuxVirtualServer.org users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [lvs-users] Real server not responding back
From: Nick Wilson <vicnickw@xxxxxxxxx>
Date: Thu, 2 Apr 2020 13:20:55 +1100
Hi Graeme,

>> 1. If you setup a tunnel without using LVS, can you get traffic to
traverse it and be seen departing the source (director) and and arriving at
the target (realserver) inside the tunnel interfaces?

To be honest, I don't know how to setup a tunnel without using LVS, and
that's why LVS/IPVS as an abstraction seemed interesting to me. Do you know
of a simple guide/tutorial I can follow for setting-up a tunnel without LVS
to test things out? I'm guessing it will involve iptables.

>> 2. If you do see that, do you have the load balanced IP address (VIP) on
the loopback adapter on the realserver?

At the moment with LVS, VIP on the real-server is not set to the loopback
interface but the tunl0 interface.

>> 3. If you do have that, is your webserver listening on that IP?

Yes, python test web server is listening on port 8000 for all interfaces
(0.0.0.0, but also tried VIP specifically). It responds fine on the
real-server IP, but doesn't even intercept the tunneled request if incoming
on VIP. However, tcpdump shows the tunneled request arrive on the
real-server, and responded back with zero-length packets until eventual
timeout.

I can ping the VIP on the real-server.

Cheers,

Nick


On Tue, 31 Mar 2020 at 22:21, Graeme Fowler <graeme@xxxxxxxxxxx> wrote:

> On 31 Mar 2020, at 08:47, Nick Wilson <vicnickw@xxxxxxxxx> wrote:
> > Please chime in if anything else comes to mind.
>
> A couple of things spring immediately to mind:
>
> 1. If you setup a tunnel without using LVS, can you get traffic to
> traverse it and be seen departing the source (director) and and arriving at
> the target (realserver) inside the tunnel interfaces?
>
> 2. If you do see that, do you have the load balanced IP address (VIP) on
> the loopback adapter on the realserver?
>
> 3. If you do have that, is your webserver listening on that IP?
>
> I have more questions dependent on the answers above. They’re all pretty
> fundamental to get this working.
>
> Graeme
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