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USG6300 L2TP packet loss

Publication Date:  2018-02-23 Views:  270 Downloads:  0

Issue Description

Customer has L2TP packet loss. The USG is used as LNS and clients are connecting to USG. Clients are connecting thru 3g/4g from mobile operators, but during tests it appeared that FTTB clients are also experiencing this issue. Looks like the issue is caused by clients increase.
When it was 250 clients, it was ok, but increasing the clients led to the packet loss increase.

Alarm Information

when ping an ip address, packet loss in tunnels increase.

PING ( 56 data bytes

Request timeout for icmp_seq 0

Request timeout for icmp_seq 1

64 bytes from icmp_seq=2 ttl=254 time=7.543 ms

Request timeout for icmp_seq 3

64 bytes from icmp_seq=4 ttl=254 time=7.803 ms

Request timeout for icmp_seq 5

64 bytes from icmp_seq=6 ttl=254 time=7.550 ms

Request timeout for icmp_seq 7

64 bytes from icmp_seq=8 ttl=254 time=7.243 ms

64 bytes from icmp_seq=9 ttl=254 time=8.049 ms

64 bytes from icmp_seq=10 ttl=254 time=8.703 ms

Request timeout for icmp_seq 11

64 bytes from icmp_seq=12 ttl=254 time=7.558 ms

64 bytes from icmp_seq=13 ttl=254 time=8.367 ms


--- ping statistics ---

14 packets transmitted, 8 packets received, 42.9% packet loss

round-trIP min/avg/max/stddev = 7.243/7.852/8.703/0.458 ms

Handling Process

1. This is a packet loss, so we configured traffic statistic, check the reason of packet loss;

2. When we configured traffic statistic and ping test again, found that the below statistic:


3.The discard detail information shown "BWM car exceed pakcets discarded", it means the bandwidth is not enough, so we check where can limit the bandwidth.

4. After check the configuration of interface that carry L2TP taffic, we found that there has configured bandwidth limit, the limit is 10k.

Root Cause

the interface configured bandwidth limit


After modify the value of the bandwidth limit, the issue is solved.


Using the taffic statistic feature check where is the  the packet loos, it can help locating the root cause.