When configuring a site-to-site policy, what must match on both sides of the tunnel to avoid negotiation errors?

In a site-to-site VPN configuration, having the LOCAL NETWORK and DESTINATION NETWORK match on both sides of the tunnel is crucial for successful connectivity and to avoid negotiation errors. The LOCAL NETWORK refers to the network behind one firewall, while the DESTINATION NETWORK is the corresponding network behind the other firewall. For the tunnel to establish correctly, both ends must be configured with appropriate address ranges that reflect their respective local and remote networks.

If there are discrepancies between these definitions on either side—a mismatched LOCAL NETWORK on one end or an incorrect DESTINATION NETWORK on the other—the devices will not recognize traffic destined for the remote end as legitimate and will therefore fail to establish or maintain the VPN tunnel. Matching these parameters ensures that both devices can effectively route traffic to and from each other's networks, facilitating seamless communication.

Other options may involve important parameters in the VPN setup, but they do not directly relate to the establishment of the tunnel itself in the same way that matching LOCAL NETWORK and DESTINATION NETWORK does. This is critical as it directly impacts whether communication can even occur through the tunnel once established.