L2TP services are interrupted because frequent 3G network disconnection


The reason is that 3G signals in the area where the device is located are poor, causing frequent 3G network disconnection. After the 3G disconnection, Hello packets expire. Consequently, the connection fails.
To address this issue, perform the following operations:
1. Configure track nqa. Restart the 3G module after the ping operation fails.
2. Change the interval for transmitting L2TP Hello packet to 120s.

Other related questions:
On a GSM network, large downstream traffic bursts cause errors in 3G data card encryption and decryption, and services are interrupted. How can I solve this problem

To solve this problem, configure configure an NQA test instance to detect the 3G link status.

  1. Run the interface cellular interface-number command to enter the 3G cellular interface view.
  2. Run the modem auto-recovery track nqa admin-name test-name [ probe-cycle period ] command to configure the device to use an NQA test instance to detect the 3G link status.
  3. Run the modem auto-recovery track action modem-reboot fail-times times command to set the maximum number of 3G link detection failures in an NQA test instance. When the number of consecutive 3G link detection failures in an NQA test instance reaches the maximum value, the device restarts the 3G data card.

How do I disconnect L2TP users on an AR
Use the following methods to disconnect L2TP users:
- Disconnect all users of the L2TP tunnel.
 1. Run the display l2tp tunnel [ tunnel-item <tunnel-id> | tunnel-name <tunnel-name> ] command in any view to check the ID of the tunnel to be terminated or remote tunnel name.
 2. Run the reset l2tp tunnel { peer-name <remote-name> | <local-id tunnel-id> } command in the user view to terminate the tunnel connection based on the local tunnel ID or remote tunnel name.
- Disconnect an L2TP user.
 1. Run the display l2tp session [ destination-ip <d-ip-address> | session-item <session-id> | source-ip <s-ip-address> ] command in any view to check the ID of the local session to be terminated based on the remote IP address.
 2. Run the reset l2tp session session-id <session-id> command in teh user view to terminate the session based on the local session ID.

When multiple branches connect to the headquarters, L2TP services are unavailable because private routes are incorrectly configured
The next hop in the static route from the LNS to the branch is incorrect. As a result, packets fail to be forwarded. Two solutions are available: 1. Configure a static route for each branch on the LNS. You need to obtain the address of the virtual template interface of a branch, and then configure a route. Because the address obtained by the virtual template interface may change, the maintenance workload is heavy. 2. Configure a dynamic routing protocol on the LNS and LAC to advertise private network segments and virtual template interface addresses and to learn the private network route to the remote end. When adding a branch, you only need to perform configurations on the LAC. The configuration does not need to be changed regardless of whether the IP address of the virtual template interface on the LAC changes. The maintenance workload is greatly reduced.

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