I apologize, if this question had already been asked and answered, but I was looking for an answer to this for a while without any luck.
The background: we have several Mikrotik routers with RouterOS v6.39.2 that are located all over the city; the routers are behind NAT and connected to our OpenVPN server that we use for management and monitoring. The protocol we use for OpenVPN is TCP, since UDP for OpenVPN is not supported by Mikrotik.
The problem: from time to time we observe response delays that occur randomly. There is no specific router or time when the issue occurs; we are constantly monitoring the CPU load and traffic and there are no anomalies on the graphs at the time this is happening, but when we simultaneously ping the OpenVPN server from the Mikrotik via public and private IP address using the Mikrotik ping utility we see that packets drop only inside the tunnel.
Here is the /etc/openvpn/server.conf
dev tun
port 1194
proto tcp
dh .key/dh1024.pem
keepalive 10 120
user nobody
group nogroup
persist-key
persist-tun
status openvpn-status.log
log-append openvpn.log
verb 3
username-as-common-name
client-config-dir /etc/openvpn/ccd
ifconfig-pool-persist ipp.txt
ca .key/ca.crt
cert .key/server.crt
key .key/server.key
server 10.48.0.0 255.255.128.0
plugin /usr/lib/openvpn/openvpn-plugin-auth-pam.so "login login USERNAME password PASSWORD"
client-cert-not-required
client-to-client
push "route 10.48.0.0 255.255.128.0"
push "route-gateway 10.48.0.1"
And here are the ping results: