problem with proxy pass

[Reinis Rozitis]

> From the hosts outside i've no connection problem, but from inside they are unable to connect to the port. No firewall are enable on Nginx LB( Centos 7 machine by the way) and Selinux is disabled.
 
By "from inside" you mean other hosts in LAN or the same centos machine?
If first then it's most likely firewall (limited outbond udp on the clients) or routing related. 

Without knowing the details/network topology there is not much to suggest - try to test if the clients can connect to any other (open) port,  icmp ping the centos machine or inspect the network activity with tcpdump.

rr