Hi Reinis,

yes, IPs exist:

ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.130 netmask 255.255.255.0 broadcast 192.168.1.255
ether fa:16:3e:1e:ad:da txqueuelen 1000 (Ethernet)
...
eth1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.131 netmask 255.255.255.0 broadcast 192.168.1.255

okay, I enabled net.ipv4.ip_nonlocal_bind=1 because nginx complained with an error message "cannot bind/assign address".
net.ipv4.ip_nonlocal_bind solved that problem.
But now with our other kernel adjustments (Reverse Path Forwarding mode 2 — Loose mode as defined in RFC 3704) this option does not have any effect.
So I disabled net.ipv4.ip_nonlocal_bind again.
But same result....upstream timed out...