I have a strange problem with one Ubuntu-system in my network. As well as some other Linux-boxes it is located in an internal network in IP range 192.168.1.x with full access to all other systems in this network and with access to the internet via a separate firewall (IP/Gateway 192.168.1.1).
All Linux-boxes are working fine except this one box (let's name it X): Internet access works properly but it can't ping or even SSH an other system in same network. On the other hand when I ping from an other system in this network to X, ping works but SSH not. Funny again: ping or SSH from X to some other server in Internet works!
Network configuration on this one system X is default/the same as on all other (as far as I can tell) Any idea what could cause this or where I could look for a reason for this strange behaviour?