[lvs-users] Real server not responding back

To: lvs-users@xxxxxxxxxxxxxxxxxxxxxx
Subject: [lvs-users] Real server not responding back
From: Nick Wilson <vicnickw@xxxxxxxxx>
Date: Thu, 26 Mar 2020 02:03:23 +1100

I'm trying to get LVS/IPVS to work for my desired configuration, but facing
a weird problem, most likely due to a simple mistake somewhere.

For now, I've created one load balancer VM (running Ubuntu 18.04 with LVS
director 1.28-3) and one real server VM (running Ubuntu 18.04).

Both the VMs are in different data-centres (different networks), so I'm
trying to make the load balancer and real server work over IP tunneling
mode based on this guide:

I've got it working to the point where if a client sends a request to load
balancer VIP, then it forwards the request to the real server, which is
running a simple HTTP web server 'python3 -m http.server 8000' (has a
'Hello World' index page), but the real server never responds back, and the
request times-out.

Using tcpdump, I can see the request hitting the director, and then hitting
the real server, and the real server responding back to the client IP with
a zero length response (ack?), that goes on for 4-5 times until timeout.
Tunneling seems to be working but the web server doesn't intercept and
respond to the request. Requesting the real server IP directly works fine

I'll appreciate if someone can share some tips or suggestions to resolve
this issue.


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