When the tunnel interface is configured in default mode, which statement about routersand the tunnel destination address is true?

When the tunnel interface is configured in default mode, which statement about routersand the tunnel destination address is true?
A . The router must have a route installed towards the tunnel destination
B . the router must have wccp redirects enabled inbound from the tunnel destination
C . the router must have cisco discovery protocol enabled on the tunnel to form a CDP neighborship with the tunnel destination
D . the router must have redirects enabled outbound towards the tunnel destination

View Answer

Answer: A

Explanation:

If routing is not carefully configured, the tunnel may have a recursive routing problem. When the best path to the "tunnel destination" is via the tunnel itself, recursive routing causes the tunnel interface to flap.

To avoid recursive routing problems, keep the control-plane routing separate from the tunnel routing using the following methods:

CUse a different autonomous system number or tag.

CUse a different routing protocol.

CUse static routes to override the first hop (but watch for routing loops).

When you have recursive routing to the tunnel destination, the following error appears:

%TUN-RECURDOWN Interface Tunnel 0 temporarily disabled due to recursive routing

http://www.cisco.com/c/en/us/td/docs/ios/12_4/interface/configuration/guide/inb_tun.html