Draytek Vigor2620 LTE Series User Manual page 87

Detection
MTU
TTL
Vigor2620 Series User's Guide
connection is alive or not through PPP Detect or Ping Detect.
Mode – Choose PPP Detect or Ping Detect for the system to
execute for WAN detection. If you choose Ping Detect as the
detection mode, you have to type required settings for the
following items.

Primary/Secondary Ping IP – If you choose Ping Detect as
detection mode, you have to type Primary or Secondary IP
address in this field for pinging.

Ping Gateway IP – If you choose Ping Detect as detection
mode, you also can enable this setting to use current WAN
gateway IP address for pinging.
With the IP address(es) pinging, Vigor router can check if
the WAN connection is on or off.

TTL (Time to Live) – Set TTL value of PING operation.

Ping Interval – Type the interval for the system to
execute the PING operation.

Ping Retry – Type the number of times that the system is
allowed to execute the PING operation before WAN
disconnection is judged.
It means Max Transmit Unit for packet.
Path MTU Discovery – It is used to detect the maximum MTU
size of a packet not to be segmented in specific transmit
path.
Click Detect to open the following dialog.
 Path MTU to – Type the IP address as the specific
transmit path.
MTU size start from – Determine the starting point

value of the packet. Default setting is 1500.
 MTU reduce size by – It determines the decreasing size
of MTU value. For example, the number specified in
this field is "8". The maximum MTU size is "1500".
After clicking the "detect" button, the system will
calculate and get the suitable MTU value such as 1500,
1492, 1484 and etc., automatically.
 Detect – Click it to detect a suitable MTU value
Accept – After clicking it, the detected value will be

displayed in the field of MTU.
Change the TTL value – Enable or disable the TTL (Time to
Live) for a packet transmitted through Vigor router.

Enable - TTL value will be reduced (-1) when it passess
through Vigor router. It will cause the client, accessing
Internet through Vigor router, be blocked by certain ISP
when TTL value becomes "0".

Disable – TTL value will not be reduced. Then, when a
packet passes through Vigor router, it will not be
cancelled. That is, the client who sends out the packet
will not be blocked by ISP.
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