The tunnel destination will be known by the tunnel interface when we do traceroute.
Please note that ospf protocol on Site A and Site B routers causes error " %TUN-5- RECURDOWN" which keep on flapping the GRE tunnel. Only upon removing the ospf configuration the GRE tunnel will become normal.

Here's the list of best practices in securing RESTful API.
1. Always Use HTTPS - Traffic must be encrypted
2. Never expose information on URLs - as this can be captured in web server logs, which makes them easily exploitable.
3. Consider Oauth
4. Adding Timestamp in Request - This will prevent very basic replay attacks from people who are trying to brute force your system
5. Input Parameter Validation - Put strong validation checks and reject the request immediately if validation fails.
6. Use Auditing and Logging - Any subject or entity can be audited