On-demand IPsec fallback connection

[towo]

Hi there, I'm currently tinkering with adopting a so-far manually managed failover connection into a more automatic one.

The edge conditions are as follows. I have two sites, let's just call them Alpha and Bravo. Alpha has 172.17.0.0/16 (as well as 172.18.0.0/16) and Bravo has 172.16.0.0/16.

There's an MPLS connection between both sites, reachable via 172.(17|16).1.100, respectively.

We also have an IPsec connection that's bolted on in case of a fallback, using the regular WAN connections of Alpha and Bravo.

What I want is: if the MPLS cross-site goes down, use the IPsec tunnel for cross-site connections.

Thus far, I've come up with the following:

• Create gateways for MPLS and IPsec

• Create a gateway group over both

• Use monitoring IP from 172.16/16 for both GWs.

• Shunt traffic into the GG using pf rulesets

Some potential problems:

• I can only create one static route for 172.16.0.0/16. Should I

  • put it on the MPLS?

  • leave it away as it will be ignored by the FW rules?

  • something entirely different?

• I can't use the same monitor IP for two gateways. Is there a better solution? The MPLS may still be down even though the router pings, for example.

• Does the monitoring actually use the gateway for pinging? Or is that attempt nonsensical?

• Will the IPsec due to policy routing just shunt everything else out of the way?

I'm feeling like I'm missing a vital trick here, any pointers - or better solutions for a redundancy failover of this kind - are appreciated.