I have a DMVPN design question. The design is Cisco ISR routes as HUB and Teltonika as Spoke. I’m running BGP over the DMVPN, and I advertise some specific route from HQ and everything works fine. But now I what to advertise an Default route, so I force all traffic over the DMVPN from the spoke point of view, but this is not working properly, I know that the Teltonika need to have en default route using the WAN / 4G Cellula outside interface to create the DMVPN tunnel. And front door VRF is not support on Teltonika, so the question is what it the best solution to solve this ? Is it to use policy-based routing and match Local LAN and force it to use next hop to be the DMVPN hub tunnel ip for traffic destined to internet ?
Because default route added on Teltonika routers by default is practically a static route with standard administrative distance value of 1 (if I remember correctly FRR considers it as directly connected route which would mean AD of 0), the easiest solution by far would be to advertise two more specific routes via BGP rather than a typical default route of 0.0.0.0/0.
Advertising 0.0.0.0/1 and 128.0.0.0/1 via BGP will ensure that AD/metric won’t be a factor and you’ll always have default default route towards your DMVPN hub, as long as BGP session is established. BGP type does not matter (can be eBGP or iBGP).
