Cisco GRE Tunnel to MikroTik Stub on Dynamic IP

This is an example of using a Site to Site with GRE over IPSEC/IKEv1 to a hub cisco router. This is not DMVPN as Mikrotik doesn't support NHRP. What this does is use the source of the tunnel as a loopback IP, and this is processed via NAT on the mikrotik to the cisco hub.

How this works

The cisco will have a dedicated Tunnel interface, and it's not multipoint GRE.

Background info and links

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/sec_conn_vpnips/configuration/zZ-Archive/IPsec_Virtual_Tunnel_Interface.html

Configuration Examples and TechNotes

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipmulti_mvpn/configuration/xe-16/imc-mvpn-xe-16-book/imc-cfg-mc-vpn.html

https://www.cisco.com/c/en/us/support/docs/routers/10000-series-routers/50421-config-register-use.html

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/interface/configuration/xe-3s/ir-xe-3s-book/ir-trsel.pdf

https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/119384-technote-ospf-00.html

https://forum.mikrotik.com/viewtopic.php?t=181900

https://forum.mikrotik.com/viewtopic.php?t=166504

https://forum.mikrotik.com/viewtopic.php?t=54870

https://forum.mikrotik.com/viewtopic.php?t=210101

https://help.mikrotik.com/docs/spaces/ROS/pages/11993097/IPsec#IPsec-Policies