350-401 Question 515
Single answerA network engineer is configuring a GRE tunnel between two branch offices. However, during testing, the tunnel fails to establish, and no traffic is passing through. Upon investigation, the engineer notices that the remote endpoint's IP address is dynamic and frequently changes. Which tunneling configuration should the engineer implement to resolve this issue?
- A
Use mGRE on both tunnel endpoints and configure NHRP for dynamic endpoint discovery.
- B
Use regular GRE and configure the remote endpoint's dynamic IP address in the tunnel source.
- C
Use DMVPN with mGRE and NHRP to support dynamic remote endpoints.
- D
Implement IPsec VPN as GRE does not support dynamic IP endpoints.
Show answer and explanation
Correct answer: C
Explanation
Dynamic Multipoint VPN (DMVPN) is the correct solution for scenarios where one or more tunnel endpoints have dynamic IP addresses. mGRE allows multiple tunnel endpoints on a single interface, and NHRP dynamically maps the public and private IP addresses of the tunnel endpoints. This combination ensures seamless communication even when the remote endpoint's IP address changes.
- A. Incorrect.
This is incorrect because mGRE alone does not solve the issue of dynamic IPs. It must be paired with NHRP to dynamically handle IP address changes.
- B. Incorrect.
This is incorrect because regular GRE requires a fixed tunnel source and destination IP address. It does not support dynamic changes in endpoint IPs.
- C. Correct.
This is correct because DMVPN combines mGRE and NHRP to support dynamic IP addresses, allowing the tunnel to establish even if one endpoint has a dynamic IP.
- D. Incorrect.
This is incorrect because while IPsec VPN supports dynamic IPs, it is not required in this scenario. The problem can be solved using DMVPN with mGRE and NHRP.