What are the four main steps in configuring a GRE tunnel over IPsec on Cisco routers?

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#1

What are the four main steps in configuring a GRE tunnel over IPsec on Cisco routers? (Choose Four)
A. Configure a physical interface or create a loopback interface to use as the tunnel endpoint.
B. Create the GRE tunnel interfaces.
C. Add the tunnel interfaces to the routing process so that it exchanages routing updates across that interface.
D. Add the tunnel subnet to the routing process so that it exchanages routing updates across that interface.
E. Add all subnets to the crypto access-list, so that IPsec encrypts the GRE tunnel traffic.
F. Add GRE traffic to the crypto access-list, so that IPsec encrypts the GRE tunnel traffic.

Correct Answer: ABDF

Explanation:
Four steps to configure GRE tunnel over IPsec are:

  1. Create a physical or loopback interface to use as the tunnel endpoint. Using a loopback rather than a
    physical interface adds stability to the configuration.
  2. Create the GRE tunnel interfaces.
  3. Add the tunnel subnet to the routing process so that it exchanges routing updates across that interface.
  4. Add GRE traffic to the crypto access list, so that IPsec encrypts the GRE tunnel traffic.

An example of configuring GRE Tunnel is shown below:

interface Tunnel0
ip address 192.168.16.2 255.255.255.0
tunnel source FastEthernet1/0
tunnel destination 14.38.88.10
tunnel mode gre ip

Note: The last command is enabled by default so we can ignore it in the configuration)

(Reference: CCNP Routing and Switching Quick Reference)