Here it comes a difficult one. We have 4 dedicated links at each site, each link with different ISP. All ISP routers are under their management so we don't have access. What we were thinking to install 2 additional routers configured with HSRP and each one connected to 2 ISPs, how would that work? The active router would track routes through each ISP connected to it and should both ISPs be down the standaby router would take over with another 2 ISPs? Would each HSRP router be able to load sharing between 2 ISPs connected to it?
To be honest it seems a little bit complicated. Are there any other solutions then that? How about one big router with 4 WAN adn 1 LAN links? I guess with one router apart from WAN redundancy we could also do load-sharing correct? But here we have single point of failure...
Now most difficult part, what VPN technology we could go for to configure VPN resiliency on all 4 ISP links? Would DMVPN or GETVPN work here?
Thanks a lot for any thoughts on that.