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> Chapter 14 - IPsec VPN > GRE over IPsec (Cisco VPN) > Overview


Cisco products that include VPN support often use Generic Routing Encapsulation (GRE) protocol tunnel over IPsec encryption. This chapter describes how to configure a FortiGate unit to work with this type of Cisco VPN.

Cisco VPNs can use either transport mode or tunnel mode IPsec. Previously, the FortiGate unit was compatible only with tunnel mode IPsec.

Example FortiGate to Cisco GRE-over-IPsec VPN

In this example, users on LAN-1 are provided access to LAN-2.