Lost telnet 25 connection to a pve.

[ozgurerdogan]

Suddenly, all vm to an other pve stop connecting on port 25. I have no firewall blocking port25, isps also checked against port blocking. But we are unable to find issue.
Server-a can connect to server-b via telnet ... 25 but not server-b.
I am not using any nat.
What else you think I could look at,. All windows and linux vms from server-b can not connecto to vms on server-a.

 

[Stefan_R]

Try running a traceroute, or check iptables/routers on all involved machines. Running tcpdump -i any port 25 might also help, run it on all involved machines along the way and see where the packet stops.

Aside from that, maybe stop using telnet? SSH does exist, is supported, and much more secure...

 

[ozgurerdogan]

Ok somehow it is fixed now. Probably at isp level issue and they fixed. Thank you for suggestion.