Draytek Vigor2500V Manual page 27

Vigor2500V series
Enter the IP address information originally provided by your ISP if you
obtained fixed IP from your ISP.
Step 5 The router will connect into your ISP "on demand". Demand is
determined as being when any LAN user tries to send data onto the
Internet. When there is no data traffic, the router will close the
connection to the ISP because there is no demand. "Idle timeout " is
determined by there being no Internet traffic for a period, for example 10
minutes. You can select 0 (zero) for no timeout-the router stays
connected once the router logs in. You can also select -1 (minus one)
which selects "Always On"—the router will try to keep a permanent
connection. The 0 and -1 settings are only recommended for AO
(always on) connections such as ADSL. You can also simply click
"Always On".
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