Hola a todos,
let me explain what happened:
I build a VPN tunnel from a remote device to my 837. I controlled all the VPN configuration and I seemed OK. But I could not try completed (my test should have been a ping from a host behind 1 device to the ethernet0 interface of the router). As there weren't any workstations connected to the switch on the rear of the router ETH0 was down. I did a workaround leaving eth0 with no ip address and giving its to a loopback interface. I completely saw that VPN was successfully configured. When I rolled back the situation (I mean deleted loopback and given its IP to eth0) I expected not to be able to ping the eth0 from remote. Magically I did! Right now I can but there are not workstation up and running (ping failed and sh arp output is empty).
How that is possible?
Alex.