In configuring a Site-to-Site policy, why is it important for the Local Network to match the Destination Network on the other side of the tunnel?

In configuring a Site-to-Site policy, having the Local Network match the Destination Network on the other side of the tunnel is crucial to avoid tunnel negotiation errors. When the two endpoints of the tunnel—typically different firewalls—are established, they need to correctly identify each other's networks for the tunnel to function properly. If the Local Network on one side does not align with the Destination Network on the other side, this mismatch can lead to difficulties in establishing the secure tunnel, preventing successful data transmission or causing dropped connections.

For a Site-to-Site VPN to work seamlessly, both devices must have a clear understanding of what networks are reachable through the tunnel. This alignment ensures that both sides can route traffic appropriately, allowing for efficient communication. If there are discrepancies in the configurations, it can lead to lengthy troubleshooting sessions and disruptions in connectivity between the sites.

In this context, while encryption, bandwidth improvement, and dynamic routing are relevant aspects of VPN configurations, the immediate issue at hand is the necessity for the network definitions to align to facilitate correct tunnel negotiations.