Chapter 10 IPsec VPN : Protecting OSPF with IPsec : Creating a redundant configuration : Adding the second IPsec tunnel
  
Adding the second IPsec tunnel
The configuration is the same as in “Configuring the IPsec VPN”, but the interface and addresses will be different. Ideally, the network interface you use is connected to a different Internet service provider for added redundancy.
When adding the second tunnel to the OSPF network, choose another unused subnet for the tunnel ends, 10.1.2.1 and 10.1.2.2 for example.