Static Point-To-Point GRE Tunnels CCIE-ENTERPRISE-INFRASTRUCTURE Practice Questions (Page 8)

Questions 36–40

1. 36application · medium

   A GRE tunnel between two routers is not coming up. The engineer checks the configuration and finds that the tunnel source is set to a physical interface that is currently down, but the router has a loopback interface that is up. What should the engineer do to bring the tunnel up?

   • AIncrease the tunnel keepalive interval to allow the tunnel to stay up even if the source is down.
   • BConfigure the tunnel destination as the loopback address of the local router instead of the remote router.
   • CChange the tunnel source to the loopback interface and ensure a route exists to reach the loopback from the remote router.
   • DAdd a static route on the local router to the remote tunnel destination via the down interface.
   Reveal Solution Discussion Select an answer first
2. 37application · medium

   A company is deploying a new branch office and needs to connect it to the headquarters over an existing IPv4 WAN. The branch will run IPv6 internally, and the headquarters also uses IPv6. The WAN provider only supports IPv4. The engineer plans to use a GRE tunnel to carry IPv6 traffic. What is the primary reason GRE is suitable for this task?

   • AGRE creates a direct Layer 2 connection, allowing IPv6 to run natively over the WAN.
   • BGRE automatically translates IPv6 addresses to IPv4 addresses, eliminating the need for NAT.
   • CGRE can encapsulate IPv6 packets inside IPv4 packets, allowing IPv6 traffic to traverse the IPv4-only WAN.
   • DGRE provides encryption, ensuring the IPv6 traffic is secure over the public WAN.
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4. 38application · medium

   An engineer is configuring a GRE tunnel between two routers. The tunnel source is set to the physical interface GigabitEthernet0/0, and the tunnel destination is the remote router's physical interface IP. The tunnel comes up, but after a few minutes it goes down. The engineer notices that the physical interface flaps occasionally. What is the best way to make the GRE tunnel more stable?

   • AIncrease the tunnel keepalive interval to 10 seconds to detect failures faster.
   • BConfigure the tunnel destination as the loopback of the remote router, but keep the source as the physical interface.
   • CUse a loopback interface as the tunnel source and ensure the remote router has a route to that loopback.
   • DAdd a static route to the remote tunnel destination via the physical interface to prevent the tunnel from going down.
   Reveal Solution Discussion Select an answer first
5. 39application · medium

   A GRE tunnel is configured between two routers, and the tunnel interface is up/up. However, the engineer cannot ping the remote loopback interface that is used as the tunnel destination. What should the engineer check first?

   • AReboot the routers to clear any stale tunnel state.
   • BVerify that the remote router has a route back to the local tunnel source IP address.
   • CEnsure the tunnel interface is configured with an IP address from the same subnet as the physical interface.
   • DCheck the tunnel keepalive settings on both routers.
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6. 40application · medium

   A GRE tunnel is configured between two sites, but large files cannot be transferred between them. Small pings succeed, but pings with a large packet size fail. The engineer suspects an MTU issue. What is the most likely cause of this problem?

   • AThe routing protocol is not advertising the tunnel network, so large packets are routed incorrectly.
   • BThe tunnel source and destination are swapped, causing packet loss for large packets.
   • CThe GRE header adds 24 bytes, reducing the effective MTU on the tunnel interface, causing fragmentation or drops.
   • DThe tunnel is not configured with a keepalive, so it drops large packets.
   Reveal Solution Discussion Select an answer first