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The goal of this tutorial is to provide a configuration for Cisco and VyOS network devices with configured PAT (Port Address Translation) that connect two remote sides A and B through point-to-point GRE tunnel encapsulated into a IPsec tunnel. In a previous tutorial we proved that GRE tunnels in conjunction with IPsec tunnels transmit multicast traffic while data integrity, authentication and confidentiality was in place. I also provided a simple configuration of GRE, IPsec tunnel and OSPF routing protocol on the Cisco and VyOS routers. In this tutorial I will go further and provide full configuration of the all network devices including PAT and access-lists.
Picture 1 - Network Topology
Topology Description - Side A
Each side has a Layer 2 Cisco switch located in a LAN network. A switch connects hosts to its switchports. Each switchport is assigned to a particular VLAN. For instance, a host PC1 is connected to the switch SW1 and the switchport is assigned to a VLAN 100. Hosts in VLAN 100 (subnet 192.168.1.0/24) have guaranteed access to a remote subnet 192.168.2.0/24 via GRE/IPsec tunnel. A NAT access-list configured on a router R1 ensures that IP address of the host in VLAN 100 is not translated by PAT when a destination address is Continue reading