I had two ubuntu servers (LB1 and LB2) which are directly connected to the internet. The servers both had ipv4 forwarding active. These two servers share their internet connection to some other servers which are only connected over a local network to LB1 and LB2. These had set the default GW to LB1 or LB2.
Suddenly without any software update or configuration changes the internet connection on the local servers stoped working. A tcpdump on lb1 or lb2 shows, that they are now using the local ip adresses, of the not directly to the internet connected servers, instead of using the external ip's of lb1 or 2.
f.e. when i'am ping 88.99.205.1 from one of the internal servers 192.168.0.61, tcpdump on lb1 on the external interface shows:
12:15:46.775516 IP 192.168.0.61 > 88.99.205.1: ICMP echo request, id 32648, seq 8, length 64
But now replay arrives. Surely the 192.168.0.61 ip is an internal one and so the accessrouter of the provider, over which lb1 and 2 are conneted to inet, drop that packages.
But the setup before runs for years without any problems. What makes it more mysterious, the same thing occour on lb2, when Iam switching the default GW of 192.168.0.61 to lb2.
So, someone had an idea how to proceed? Thank you very much!
