3Com 10014299 manual Troubleshooting L2TP

Troubleshooting L2TP 633

■Errors occur to user name and password set at LAC, or the corresponding user information is not set at LNS.

■LNS cannot allocate addresses, e.g., the address pool is set too small, or is not set at all.

■The types of tunnel password authentication are inconsistent. Given that the default authentication type of VPN connection created by Windows 2000 is MSCHAP, if the peer does not support MSCHAP, CHAP is recommended.

Fault 2: After a tunnel is created, the data cannot be transmitted, for example, ping operation fails.

Troubleshooting: The reasons may be as follows:

■The address of LAC is configured incorrectly: Generally, LNS distributes addresses, but LAC can also specify its own address. If the specified address and the address to be allocated by LNS are not in the same segment, this problem will occur. It is recommended that LNS allocate the addresses for LAC.

■Network congestion may occur to backbone network and a lot of packets are dropped. L2TP transmission is based on UDP (User Datagram Protocol) and UDP does not control message errors. If L2TP is adopted on the paths where line quality is not guaranteed, the ping command will not take effect occasionally.