Before entering this question I browsed all Teltonika "self service" resources ( FAQ, wiki etc. ) without finding a clear answer.
I should connect a RUT950 ( version RUT9XX_R_00.06.06.1 ) via its 4G uplink ( with dynamic and private IP beyond NAT: the LTE provider does not grant public and static IP ) to a Cisco VPN IPsec concentrator ( using IKE version 1 and FQDN settings ).
Here ( https://wiki.teltonika-networks.com/view/RUT950_VPN#IPsec_configuration ) I read that "IKEv1 only supports IP address ID selector" and "FQDN only supported with IKEv2".
Is it a peculiar limitation of Teltonika devices or a "natural" limitation of IKEv1 ( therefore can not be overcome by Teltonika unless my user will move its tunnels to more recent IKEv2 ) ?
In fact the example https://wiki.teltonika-networks.com/view/Setting_up_an_IPsec_tunnel_between_RUT_and_Cisco_device uses IKEv1 and IP address of the involved routers ( not their FQDN ).
Anyway I will try to upgrade RUT950 to latest RUT9XX_R_00.06.07 improving these features: improved IPsec and DMVPN pre-shared key validation, fixed IPsec identifier validation and removed "Aggressive mode" choice from IPSec IKEv2
Any troubleshooting idea is welcome !
Many thanks in advance.