Why pinging 127.0.0.1 on OpenVPN-Server does not work when a client is connected? (Windows)

UltraFine

Summary:

When I boot up my server box with OpenVPN installed and ping 127.0.0.1 it works, but as soon as a client connects to the box pinging 127.0.0.1 on the server becomes impossible? Even after client disconnects from OpenVPN, I cannot ping 127.0.0.1 anymore.

Who knows why and how to fix that?

Setup:
LAN-Adapter: 192.168.2.140
OPenVPN-Adapter: 10.8.0.1

TinCanTech

This is the first ever report of such an issue ..

UltraFine

Here is a pic.

https://ibb.co/6ZgxWzH
https://ibb.co/6ZgxWzH

I actually tried this on two different server boxes. One is a VM (at location A) and another is a real box (at location B). Both had the same result.

UltraFine

Server config:


port 7777
proto tcp4
tcp-queue-limit 256 
dev tun
ca "C:\\Program Files\\OpenVPN\\config\\ca.crt"
cert "C:\\Program Files\\OpenVPN\\config\\server.crt"
key "C:\\Program Files\\OpenVPN\\config\\server.key"
dh "C:\\Program Files\\OpenVPN\\config\\dh2048.pem"
topology subnet
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt
client-config-dir "C:\\Program Files\\OpenVPN\\config\\ccd"
keepalive 10 120
tls-auth ta.key 0 # This file is secret
cipher AES-256-CBC
persist-key
persist-tun
status openvpn-status.log
verb 5
explicit-exit-notify 0
push "redirect-gateway def1"
push "remote-gateway 10.8.0.1"
push "dhcp-option DNS 10.8.0.1"
keepalive 10 60

TinCanTech

UltraFine wrote push "remote-gateway 10.8.0.1"

This is incorrect. You probably mean --route-gateway .. although, you don't need that either.

I notice in your screen shot that you have two wintun adapters, do you have other VPNs running at the same time ?

UltraFine

TinCanTech wrote
UltraFine wrote push "remote-gateway 10.8.0.1"
This is incorrect. You probably mean --route-gateway .. although, you don't need that either.

I notice in your screen shot that you have two wintun adapters, do you have other VPNs running at the same time ?

No, I have one TUN-Adapter. One entry is for IPv4 , the other one is for IPv6, I suppose.

TinCanTech

UltraFine wrote No, I have one TUN-Adapter.

Technically, wintun

UltraFine wrote One entry is for IPv4 , the other one is for IPv6, I suppose

Yes, powershell iterates things differently ..

UltraFine wrote push "dhcp-option DNS 10.8.0.1"

I presume your server is a DNS server also ?

UltraFine

TinCanTech wrote I presume your server is a DNS server also ?

No, it is not. You are right, this is probably a misconfiguration. But it should not effect the ping of localhost on the server.

TinCanTech

UltraFine wrote it should not effect the ping of localhost on the server

To my knowledge, the only way for ping 127.0.0.1 to fail is to block it with a firewall.

UltraFine

TinCanTech wrote
UltraFine wrote it should not effect the ping of localhost on the server
To my knowledge, the only way for ping 127.0.0.1 to fail is to block it with a firewall.

I agree. I had the same thought. But I disabled the firewall using following line

powershell Set-NetFirewallProfile -Profile Domain,Public,Private -Enabled False

and localhost still does not ping.