OK so per your suggestions I have changed to a more conventional configuration. I did a hard reset and started all over. Now the WAN is eth0, and the LAN is eth4, and the switch is in normal operation. Configuration file attached. Unfortunately there is no improvement. The L2TP speed is still 10X slower than the VPN on my 10+ year old TZ170. Please any suggestions for further troublehooting.
EdgeRouter PoE with v1.9.1. The typical use case is remote access from a Win 7 PC, with Remote Desktop to a LAN Win 7 PC, and filesystem mounting of a LAN Win 7 PC and/or Netgear NAS.
This is what I have tried:
1. Tried PPTP instead - slow also.
2. Mounted a Mac filesystem instead - slow also.
3. Checked EdgeRouter CPU usage - very low so this is not the bottleneck.
4. For the Win 7 PC filesystem case, did a WireShark on the LAN side to see what was going on. A sample is below. 168.6 is the remote PC, 168.31 is the LAN PC with the filesystem. To me it seems all the "DUP ACK" and "Retransmission" indicate something is getting very clogged up. But this would be the symptoms or side effect of whatever the real problem is.
5. Swapped in SonicWall TZ170 - same everything else. TZ170 is 10X faster.
Please, any suggestions for further troubleshooting, thank you kindly.
4373 20.176338 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4374 20.176530 192.168.168.6 192.168.168.31 TCP 60 50646 > microsoft-ds [ACK] Seq=4096 Ack=3088734 Win=16660 Len=0
4375 20.176559 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4376 20.176567 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4377 20.199067 192.168.168.6 192.168.168.31 TCP 66 [TCP Dup ACK 4374#1] 50646 > microsoft-ds [ACK] Seq=4096 Ack=3088734 Win=16660 Len=0 SLE=3090094 SRE=3091454
4378 20.199104 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4379 20.202545 192.168.168.6 192.168.168.31 TCP 74 [TCP Dup ACK 4374#2] 50646 > microsoft-ds [ACK] Seq=4096 Ack=3088734 Win=16660 Len=0 SLE=3092814 SRE=3094174 SLE=3090094 SRE=3091454
4380 20.202573 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4381 20.204216 192.168.168.6 192.168.168.31 TCP 82 [TCP Dup ACK 4374#3] 50646 > microsoft-ds [ACK] Seq=4096 Ack=3088734 Win=16660 Len=0 SLE=3095534 SRE=3096894 SLE=3092814 SRE=3094174 SLE=3090094 SRE=3091454
4382 20.204246 192.168.168.31 192.168.168.6 TCP 1414 [TCP Fast Retransmission] [TCP segment of a reassembled PDU]
4383 20.204278 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4384 20.224376 192.168.168.6 192.168.168.31 TCP 82 [TCP Dup ACK 4374#4] 50646 > microsoft-ds [ACK] Seq=4096 Ack=3088734 Win=16660 Len=0 SLE=3095534 SRE=3098254 SLE=3092814 SRE=3094174 SLE=3090094 SRE=3091454
4385 20.224415 192.168.168.31 192.168.168.6 TCP 1414 [TCP Retransmission] [TCP segment of a reassembled PDU]
4386 20.224451 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4387 20.228514 192.168.168.6 192.168.168.31 TCP 82 [TCP Dup ACK 4374#5] 50646 > microsoft-ds [ACK] Seq=4096 Ack=3088734 Win=16660 Len=0 SLE=3095534 SRE=3099614 SLE=3092814 SRE=3094174 SLE=3090094 SRE=3091454
4388 20.228543 192.168.168.31 192.168.168.6 TCP 1414 [TCP Retransmission] [TCP segment of a reassembled PDU]
4389 20.228574 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4390 20.229760 192.168.168.6 192.168.168.31 TCP 90 [TCP Dup ACK 4374#6] 50646 > microsoft-ds [ACK] Seq=4096 Ack=3088734 Win=16660 Len=0 SLE=3057454 SRE=3058814 SLE=3095534 SRE=3099614 SLE=3092814 SRE=3094174 SLE=3090094 SRE=3091454
4391 20.231155 192.168.168.6 192.168.168.31 TCP 74 50646 > microsoft-ds [ACK] Seq=4096 Ack=3091454 Win=16660 Len=0 SLE=3095534 SRE=3099614 SLE=3092814 SRE=3094174
4392 20.231552 192.168.168.6 192.168.168.31 TCP 66 50646 > microsoft-ds [ACK] Seq=4096 Ack=3094174 Win=16660 Len=0 SLE=3095534 SRE=3099614
4393 20.231553 192.168.168.6 192.168.168.31 TCP 60 50646 > microsoft-ds [ACK] Seq=4096 Ack=3099614 Win=16660 Len=0
4394 20.231772 192.168.168.6 192.168.168.31 TCP 66 [TCP Dup ACK 4393#1] 50646 > microsoft-ds [ACK] Seq=4096 Ack=3099614 Win=16660 Len=0 SLE=3088734 SRE=3090094
4395 20.248750 192.168.168.6 192.168.168.31 TCP 66 50646 > microsoft-ds [ACK] Seq=4096 Ack=3100974 Win=16660 Len=0 SLE=3091454 SRE=3092814
4396 20.248781 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4397 20.252956 192.168.168.6 192.168.168.31 TCP 66 50646 > microsoft-ds [ACK] Seq=4096 Ack=3102334 Win=19380 Len=0 SLE=3094174 SRE=3095534
4398 20.252985 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4399 20.273185 192.168.168.6 192.168.168.31 TCP 60 50646 > microsoft-ds [ACK] Seq=4096 Ack=3105054 Win=18700 Len=0
4400 20.273218 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4401 20.273227 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4402 20.273231 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4403 20.301246 192.168.168.6 192.168.168.31 TCP 60 50646 > microsoft-ds [ACK] Seq=4096 Ack=3107774 Win=18020 Len=0
4404 20.301293 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4405 20.301301 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]
4406 20.301497 192.168.168.6 192.168.168.31 TCP 60 50646 > microsoft-ds [ACK] Seq=4096 Ack=3110494 Win=18020 Len=0
4407 20.301527 192.168.168.31 192.168.168.6 TCP 1414 [TCP segment of a reassembled PDU]