My Internet connectivity is currently via a DOCSIS cable modem in bridge mode. It's supplied by the ISP and I can't do much to change its configuration. The link is not very reliable, it's prone to short (~5 minute) outages multiple times per day. When it works, the bandwidth is good. The tech support of the ISP is entirely useless.
When the connection fails, the link stays up but packet traffic (all IP, even ARP) stops. Well, I no longer receive packets. There's no way for me to tell whether any packets I send are getting out. While getting the ISP to fix this would be optimal, I have given up trying to work with their tech support.
I'm considering using a second ISP for fail-over. The second ISP offers a much lower bandwidth solution that I assume is VDSL2-based (the sales person described it as VDSL, but they stated that the bandwidth is 90Mbit). There are no other ISPs offering connectivity in this area (residential or business, as far as I can tell).
I'm currently using a Linux box to provide IPv4 NAT for the DOCSIS ISP (no IPv6 since the ISP only offers IPv6 DS-lite and I don't fancy using their CGNAT for IPv4 connectivity).
Can you point me to an example working configuration for network connectivity failover in this kind of situation?
I assume a simple implementation of this would involve a change of IPv4 source address on my Linux-based SNAT router, breaking TCP connections (so e.g. I'd need to re-connect to zoom meetings when there is a failover, and VoIP calls will drop). Can you show me (e.g. via hyperlink) a worked example of a configuration which mitigates this problem? For example, is there an option which is simpler than using a remote VPN server? If VPN is my best option, can you point me to a worked example?
Is ISP-Balance still the recommended solution? Is there an example anywhere of using this with VPN solutions other than OpenVPN (e.g. NordVPN)? Are there good alternatives to ISP-Balance?
