Free Cisco 300-410 ENARSI Actual Exam Questions - Question 2 Discussion
An administrator is configuring a GRE tunnel to establish an EIGRP neighbor to a remote router. The
other tunnel endpoint is already configured. After applying the configuration as shown, the tunnel
started flapping. Which action resolves the issue?
A imo, the tunnel keeps flapping because the tunnel destination IP is getting routed inside the tunnel itself. Stopping that route from being advertised should fix the loop and stabilize the tunnel.
Makes sense that the tunnel flaps because the tunnel source or destination IP is within the tunnel subnet, causing a routing loop. So, option A looks right — stop sending a route matching the tunnel destination across the tunnel. That usually avoids the source/destination confusion and stabilizes the tunnel. D might help in some cases, but if the problem is routing the tunnel endpoint IP inside the tunnel itself, removing that route should fix it quicker.
Maybe D, since /31 is the usual mask for point-to-point tunnels to avoid overlaps.
A. The main problem with GRE tunnels flapping like this often comes from the tunnel interface trying to send traffic destined to its own tunnel endpoint over the tunnel itself, causing a loop. Stopping the route that matches the tunnel destination from being sent through the tunnel prevents this feedback loop and stabilizes the connection. The other options don’t directly address the core cause of the flapping, which is the loop created by routing the tunnel endpoint IP back into the tunnel interface.
It’s A because sending the tunnel destination route over the tunnel causes routing loops and flapping.
A/D? Not sure if sending a route matching the tunnel destination causes looping or if the /31 netmask is required here. Need more details on how the tunnel IPs are set.