OVH Dedicated Server, SSH suddenly stops working

Did you whitelist IPs ?

CSF firewall related CSF - CSF Firewall info | Centmin Mod Community and CSF Firewall - Centmin Mod - Menu based Nginx installer for CentOS servers

more info might be helpful

1. What version of Centmin Mod ? .07 stable or .08 beta ? If .08 beta when was it installed and when was last time you updated the .08 beta code (there's constant updates to the code).
2. What's your VPS/Server hardware specifications ? Xen/KVM/OpenVZ ? cpu type ? memory available ? disk space ? OS and version ? i.e. CentOS 6.6 or 7.1 ?
3. Who's your web host ?
4. Your ISP ip address static/dynamic ?
5. What were you doing connection wise to your server leading up to the blockage ?
6. If you're on dynamic ip, you may need additional steps CSF Firewall as per Getting Started Guide step 4
7. Other steps: Does your web host offer out of band VNC/KVM/IPMI Console access? If you can, check if you ips are blocked using csf -g grep command
   
   Code:

   csf -g YOURIPADDRESS

   commands you can see for csf via
   
   Code:

   csf -h

   whitelist your ISP range of ips if you know the range
   
   Code:

   csf -a IPADDRESSORRANGE

   remove temp and permanent blocks from csf
   
   Code:

   csf -tr IPADDRESS
   csf -dr IPADDRESS

   also check CSF /var/log/lfd.log for clues
   
   Code:

   tail -50 /var/log/lfd.log

   another log is /var/log/messages you can grep it for your ips
   
   Code:

   grep IPADDRESS /var/log/messages

 

can you do the reverse and ssh and ping your other systems and yourself via OVH server SSH ?

Did you change SSH port number from 22 ?

 

enable SSH client verbose mode when you connect for further clues too

 

and your /var/log/secure for clues

 

your secure log says sshd listening on port 1018 but here you trying port 2222 ?

 

you testing with CSF enabled ? if you disable CSF firewall, you want have any default iptable rules in place so alot of stuff might be blocked port wise

With CSF enabled, I'd double check your ports are whitelisted for SSHD port

Code:

egrep '^TCP_|^TCP6_|^UDP_|^UDP6_' /etc/csf/csf.conf

and check listening ports

Code:

netstat -ntl