We have one server that is connected to two independent networks through two NICs.
Network A and Network B
The server gets two IPs - but those IPs are in completely different networks. So far everything is fine - and the server can be accessed from both networks without any problem.
Now - in network A we are also providing a public IP (handled by a Firewall - no configuration of public IP on server) to the server, so that the server can be seen from the outside. That does not happen in network B. Also this works initially - so our server can be seen from outside and from the two internal networks - and everything works fine...
Internally our DNS servers make sure that we browse internally - but we could also access the network from all networks through the internet.
Just after a while, the public IP stops working - no ping nothing. Then - if I take the NIC of network B down and up again, it works.
What could be the problem?
## This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). # The loopback network interface auto lo iface lo inet loopback # The primary network interface allow-hotplug eth0 iface eth0 inet static address xxx.xxx.7.41 netmask 255.255.255.0 broadcast xxx.xxx.7.255 gateway xxx.xxx.7.254 dns-nameservers xxx.xxx.7.17 126.96.36.199 188.8.131.52 184.108.40.206 # The secondary network interface allow-hotplug eth1 iface eth1 inet static address xxx.xxx.20.9 netmask 255.255.255.0 broadcast xxx.xxx.20.255 gateway xxx.xxx.20.1 dns-nameservers xxx.xxx.10.12 220.127.116.11 18.104.22.168`