In this scenario, there are three probable causes for the issue of users not being able to access external websites from their browsers after attempting to steer traffic to Netskope using GRE tunnels. One cause is that the configured GRE peer in the Netskope platform is incorrect, which means that the Netskope POP that is supposed to receive the GRE traffic from the customer’s network is not matching the IP address of the customer’s router that is sending the GRE traffic. This will result in a failure to establish a GRE tunnel between the customer and Netskope. Another cause is that the corporate firewall might be blocking GRE traffic, which means that the firewall rules are not allowing the GRE protocol (IP protocol number 47) or the UDP port 4789 (for VXLAN encapsulation) to pass through. This will result in a failure to send or receive GRE packets between the customer and Netskope. A third cause is that the route map was applied to the wrong router interface, which means that the configuration that specifies which traffic should be steered to Netskope using GRE tunnels was not applied to the correct interface on the customer’s router. This will result in a failure to steer the desired traffic to Netskope. The pre-shared key for the GRE tunnel is incorrect is not a probable cause for this issue, as GRE tunnels do not use pre-shared keys for authentication or encryption. Netskope does support GRE tunnels, so this is not a cause for this issue either. References: [Netskope Secure Forwarder], Netskope Security Cloud Operation & Administration (NSCO&A) - Classroom Course, Module 3: Steering Configuration, Lesson 3: Secure Forwarder.