I was looking into a way to have multi-homing without BGP (due to being a residential customer) and without the use of NAT. I feel like the IPv6 “native” way would have been advertise both prefixes and then give the control to the router on how they are used, all new connections go to ISP1 (or 2 depending on admin choice), inbound ISP1 go to ISP1 gateway, inbound ISP2 go to ISP2 gateway.
From my understanding this isn’t so easy, you may have DRP (Default Router Priority) but what if you are using LTE passthrough and both prefixes are being advertised by the same router? Then I came across RFC8475 https://datatracker.ietf.org/doc/html/rfc8475 which answers what I’ve been looking for.
It gives you the ability (without scripting) to advertise a prefix / invalidate a prefix based on network changes.
The example it gave was “Send RAs triggered by defined event policies in response to an uplink status change event” which those changes could be any of the following
- Uplink interface status change;
- Presence of a particular route in the routing table;
- Presence of a particular route with a particular attribute (next hop, tag, etc.) in the routing table;
- Protocol adjacency change.