Problem: No Connection from LAN but WAN Works

networking
openvpn
problem

#1

Problem

You can not reach you local UCS host from within the LAN. From the Internet access works fine.

Investigation

The server can not be reached by any tools. But all services (mail, ssh, …) can be used when trying to connect from external Internet (through a port forwarding router) or through the configured OpenVPN connection.
Using “ping” from the local network it does not get any replies:

root@any:~# ping ucs
PING ucs.multi.ucs (192.168.19.100) 56(84) bytes of data.
^C
--- ucs.multi.ucs ping statistics ---
5 packets transmitted, 0 received, +3 errors, 100% packet loss, time 4101ms
pipe 4

The “arp” command afterwards shows the correct IP <-> MAC mapping but can not resolve the hostname:
? (192.168.19.100) at 00:1a:8c:13:aa:87 [ether] at eth1
From within the UCS host you are not able to ping any host- not even the above mentioned router.

The routing tables shows:

root@ucs:~# route -n
Kernel-IP-Routingtable
Ziel            Router          Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.19.1    0.0.0.0         UG    0      0        0 eth1
172.17.0.0      0.0.0.0         255.255.0.0     U     0      0        0 docker0
192.168.9.0     10.20.30.1      255.255.255.0   U     0      0        0 tun0
192.168.9.0     0.0.0.0         255.255.255.0   U     0      0        0 eth1

So all packets for the local network were sent out through the OpenVPN interface and thus never reached the loccal network.

Solution

The OpenVPN app was misconfigured. In the file /etc/openvpn/server.conf remove (or comment out) the following entry:
route 192.168.9.0 255.255.255.0 10.20.30.1

Then delete the local route:

ip route del 192.168.19.0/24 via 10.20.30.1 dev tun0

And restart OpenVPN service.

Afterwards, check you OpenVPN configuration in UMC which caused the invalid routing entry.


#2