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L2TP dialing prompt consultation timeout fault

Publication Date:  2012-12-18 Views:  1829 Downloads:  0

Issue Description

Use the VPN Client client L2TP dialing prompt keepalive timeout timeout or consultation, dial failed.

Alarm Information

Prompt " tunnel keepalive time-out  or Negotiation time-out ".

Handling Process

In this case, check the client configuration, found the LNS gateway address configuration is incorrect, the LNS gateway address should be configured on the LNS device physical interface address, which in this case is the configuration of the LNS devices in the Virtual-Template virtual template address, resulting in LNS gateway cannot respond to a L2TP connection request.Modify the LNS gateway address for the LNS device interface address, and then dialing test, dialing success.

Root Cause

If the dial when this error, general consultation timeout, LNS is the main gateway is not caused by the response, basically have the following reason:
1) to the LNS gateway address network unreachable, so it is necessary to check the client to the LNS gateway routing accessibility, you can use the Ping or tracert test LNS gateway connectivity status.
2) to the LNS gateway 1701 UDP port unreachable, may be an intermediate network device blocked the port message.
3) the client configuration LNS gateway address error, does not actually is or was a non LNS gateway address and does not respond to the L2TP connection request.If the dial is connected, the emergence of this message the network interruption, in the specified time is not received keep-alive message which led to the failure of connection.


Understanding of LNS gateway address refers to a device interface address rather than the LNS VT virtual template address.