Got to work IPS and IDS-system Snort, adding the sensor to the external IP of Endian-gateway. That is, now two sensors are configured - one on the surveillance of the local, the other for external interfaces.
The contents of the file "/etc/snort/vars.tmpl":
"
var HOME_NET [$HOME_NET,xx.xx.xx.xx]
var DNS_SERVERS [$DNS_SERVERS]"
, where
xx.xx.xx.xx - external IP of my Endian Firewall