R3721-F3210-F3171-HP High-End Firewalls VPN Configuration Guide-6PW101

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LNS to check whether the expected routes are present. If not, configure a static route or configure
a dynamic routing protocol.
2. Congestion occurs on the Internet backbone and packet loss ratio is high. L2TP data transmission
is based on UDP, which does not provide the packet error control function. If the line is unstable,
the LAC and LNS may be unable to ping each other and L2TP applications may fail.