I have a VPS with two IP addresses: and If you ping them, you'll find they are both responding. I can also ping google.com etc. from either of them.

But I cannot ping one from the other. I can't ping localhost. I can't establish any TCP connections between server and client apps on the same box (though I can connect to those same servers from elsewhere).

I'm stumped. This change came suddenly after something happened to cause one of the venet0 interfaces to disappear, so most things are still configured as if connection between them were possible. For instance, my iptables configuration isn't causing this problem as it is the same one that worked great with everything before.

What might cause such a strange problem and what can I do?

  • 2
    paste "ip link show", "dmesg | grep venet0", what is in /proc/net/dev ? Also was the server ever rebooted? Can you show /etc/udev/rules.d/##-persistent-network-rules? And we'll go from there. – Danila Ladner May 3 '13 at 4:36
  • Ensure there's an iptables rule to accept incoming packets over the loopback interface. iptables -I INPUT -i lo -j ACCEPT Will add it if not. Be sure to save the rule with service iptables save for your distribution. – Andrew Ty. May 3 '13 at 5:05

Have you checked in server firewall, Ip should not block in each other's firewall, check as below:

in iptables

iptables -nL |grep IP

in csf

grep /etc/csf/*

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.