Which parameter must match on all routers in a DMVPN Phase 3 cloud?
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A. B. C. D.A.
In a DM VPN Phase 3 cloud, the parameter that must match on all routers is the NHRP (Next Hop Resolution Protocol) network ID.
A DM VPN (Dynamic Multipoint VPN) is a technique used to establish a secure VPN (Virtual Private Network) over the public internet. DM VPN Phase 3 is an advanced implementation of DM VPN that uses the NHRP protocol to allow for a more scalable and dynamic network design.
NHRP is used to map a tunnel IP address to a physical IP address of the next-hop device in the network. In DM VPN Phase 3, each router is assigned a unique NHRP network ID, which is used to identify the network to which it belongs. When a router needs to communicate with another router in the same network, it sends an NHRP registration request to the NHRP server, which responds with the physical IP address of the next-hop device. The router can then establish a direct connection to the next-hop device and create a GRE (Generic Routing Encapsulation) tunnel for secure communication.
Therefore, in a DM VPN Phase 3 cloud, it is essential that all routers have the same NHRP network ID configured to enable efficient communication and mapping between the tunnels. The GRE tunnel key is used to identify the GRE tunnel between two routers, while the tunnel VRF (Virtual Routing and Forwarding) is used to isolate traffic between different VPNs. The EIGRP (Enhanced Interior Gateway Routing Protocol) split-horizon setting is used to prevent routing loops in a network.
Hence, option B, NHRP network ID, is the correct answer.