We noticed that Windriver is unable to ping the public IP addresses of router-002 and router-003. However, GRE tunnel creation is successful, and tunnel connectivity works with router-002, although pinging its public IP is still unsuccessful.

When creating a GRE tunnel to the alias IP of ysul as an endpoint the tunnel is unpingable however when creating the GRE tunnel using the public IP of ysul, GRE tunnel responds well to ping.
I suspect that the problem might come from using an alias IP as GRE endpoint that might cause this as it suggest encapsulation/decapsulation issues

I created and tested a Salt reactor that listens for the carp/master event sent by the routers. For now, the reactor only runs a test command on Ysul and Windriver to confirm that the event is correctly received and that the master can trigger actions on those hosts.

Test to validate Salt event emission and reception on the master :

This explanation is not fully correct. Indeed the VIP cannot be used to establish two GRE tunnels at the same time on Windriver or on Ysul.

This issue is indeed not longer relevant.

@dereckson I tried applying these units for role devserver: