When the EIGRP Router ID is not manually configured, which interface is used next to determine the Router ID?

When the EIGRP Router ID is not manually configured, which interface is used next to determine the Router ID?

• A. Highest IP address on a loopback interface
• B. Lowest IP address on a loopback interface
• C. Highest IP address on a physical interface
• D. Highest IP address on a virtual interface

Answer: (A)

The Router ID in EIGRP (Enhanced Interior Gateway Routing Protocol) is a critical component used to uniquely identify each router within an EIGRP routing domain. When a Router ID is not manually set by the network administrator, the EIGRP process looks for an appropriate value to use based on the addresses of the router's interfaces. In scenarios where no loopback interface is configured, the EIGRP process will select the highest IP address assigned to any physical interface on the router. However, when a loopback interface is present, the rule changes to prioritize loopback interfaces over physical ones due to their inherent stability and reliability. The configuration considers the highest IP address assigned to that loopback interface as the Router ID. Assigning the Router ID using a loopback interface ensures consistency since loopback interfaces are not affected by operational status (i.e., they remain up unless explicitly shut down). This makes them ideal for stable identification across the network. Thus, in the absence of a manually configured Router ID, the correct path for determining the Router ID is to first inspect loopback interfaces, leading to the conclusion that the highest IP address on a loopback interface is the attribute selected by EIGRP. This ensures that the Router ID remains consistent and reliable

The Router ID in EIGRP (Enhanced Interior Gateway Routing Protocol) is a critical component used to uniquely identify each router within an EIGRP routing domain. When a Router ID is not manually set by the network administrator, the EIGRP process looks for an appropriate value to use based on the addresses of the router's interfaces.

In scenarios where no loopback interface is configured, the EIGRP process will select the highest IP address assigned to any physical interface on the router. However, when a loopback interface is present, the rule changes to prioritize loopback interfaces over physical ones due to their inherent stability and reliability. The configuration considers the highest IP address assigned to that loopback interface as the Router ID.

Assigning the Router ID using a loopback interface ensures consistency since loopback interfaces are not affected by operational status (i.e., they remain up unless explicitly shut down). This makes them ideal for stable identification across the network.

Thus, in the absence of a manually configured Router ID, the correct path for determining the Router ID is to first inspect loopback interfaces, leading to the conclusion that the highest IP address on a loopback interface is the attribute selected by EIGRP. This ensures that the Router ID remains consistent and reliable