https://www.cisco.com/c/en/us/support/docs/smb/routers/cisco-rv-series-small-business-routers/kmgmt-2336-RV34x-L2TP-IPSec-fails-when-router-is-behind-NAT-device.html
RV34x: L2TP/IPsec fails when router is behind NAT device - Cisco
This document is a workaround when L2TP/IPsec fails when a RV34x series router is behind a NAT device.
l2tp ipsecnat devicefails
https://www.earth.li/mailman3/hyperkitty/list/main@lists.alug.org.uk/message/UQLYN6QPMCZZO63Y6IKABCQ3TTX663XR/
Re: [ALUG] SSH Connection to device behind NAT/firewall - main - earth.li