SMC Networks BR21VPN - annexe 1 Manual page 56

STEP 2﹒Setting the Connection Service (ICMP or DNS way)：
ICMP：Enter an Alive Indicator Site IP (can select from Assist)
(Figure3-3)
DNS：Enter DNS Server IP Address and Domain Name (can
select from Assist) (Figure3-4)
Setting time of seconds between sending alive packet.
Connection test is used for SMC BR21VPN to detect if the WAN can connect or
not. So the Alive Indicator Site IP, DNS Server IP Address, or Domain Name must
be able to use permanently. Or it will cause judgmental mistakes of the device.
Figure3-3 ICMP Connection
Figure 3-4 DNS Service
55