You can't just pick random numbers to start at eg. 192.168.128.10 because subnetting does not work that way ie, you can't use 192.168.128.1 - 4 as one subnet and then use 192.168.128.10 -> 150 for another subnet because it won't work.    If you really need 140 IPs in a subnet then you need to use the whole 192.168.128.0/24 subnet for those IPs and then you would need another 192.168.x.0/24 subnet for core devices etc.    When you subnet first work out how many IPs you need and that will tell you what subnet mask to use and also what is left to use for other subnets.   Jon ... View more

  I think you need to do as Rick suggests and use IP SLA to track an IP address on the internet and if that IP becomes unreachable then you can install a static route for private link.    See this link for an example -    https://blog.ipspace.net/2007/08/install-static-route-when-ip-address-is.html   Jon ... View more

  I still think you are seeing this a routing issue when it is more to do with how the servers know to switch between the use of public or private IPs and how that happens which is nothing to do with the network.    You could already have the routes in place for the private IPs to be used when needed but how do the servers know when to use them.    Jon ... View more

  The default decrement value is 10 but it can be any value between 1 - 255.    So as long as you subtract a large enough number to make your standby preempt then you can use any numbers within the accepted range you like.    Jon ... View more

  Not sure I follow.    Firstly does the VPN not run across the internet and if so if you lose the internet you lose the VPN as well.    Secondly if it is does not run across the internet then it seems to be more a question as to how to tell the servers which IPs to use rather than a routing issue.    A better understanding of your topology would help.    Jon ... View more