A network administrator runs show ip route and notices that the same destination network is being advertised by both RIP and EIGRP. In the routing table, the route is installed as an EIGRP route. Why is the RIP route not used?

Introduction / Context:
Cisco routers can run multiple routing protocols at the same time, such as Routing Information Protocol and Enhanced Interior Gateway Routing Protocol. When more than one protocol learns a route to the same destination network, the router must choose which route to install in the routing table. Understanding the concept of administrative distance is crucial, because it determines which protocol is trusted more when there is competing route information. This question examines why an EIGRP route is chosen over a RIP route for the same destination.

Given Data / Assumptions:

• The router is running both RIP and EIGRP.
• The same destination network is learned via both protocols.
• The show ip route output shows the route marked as an EIGRP route.
• There are no hints of misconfiguration such as obvious routing loops in the description.

Concept / Approach:
Administrative distance is a Cisco specific value that expresses how trustworthy a route source is. A lower administrative distance indicates a more trusted source. When a router learns the same prefix from multiple sources, it compares their administrative distances before considering metrics inside each protocol. Default administrative distances are well known: connected routes are 0, static routes are 1, EIGRP is 90 for internal routes, OSPF is 110, and RIP is 120. Therefore, when both EIGRP and RIP provide a route to the same destination, the router prefers EIGRP because 90 is lower than 120.

Step-by-Step Solution:
1. Identify that the same network prefix appears in advertisements from both RIP and EIGRP. 2. Recall default administrative distances: EIGRP internal routes use distance 90 and RIP uses distance 120. 3. When multiple protocols advertise the same route, Cisco routers choose the one with the lowest administrative distance. 4. Compare the distances: 90 for EIGRP is lower than 120 for RIP. 5. Therefore, the router installs the EIGRP route in the routing table and the RIP route is ignored, although it can still be seen in debugging or protocol specific outputs.

Verification / Alternative check:
You can verify this behaviour by using show ip route and show ip protocols. Show ip route will mark the active route with the code D for EIGRP and R for RIP, but only the D route will appear as active for that prefix. Show ip protocols displays the default administrative distances for each protocol. Additionally, you can manually change administrative distances with distance commands under routing process configuration to observe how the chosen route changes if EIGRP is made less trusted than RIP. This confirms that administrative distance, rather than metrics, is the primary factor when routes from different protocols compete.

Why Other Options Are Wrong:
EIGRP has a faster routing update timer than RIP: Update frequency does not control which route is placed in the table when the same prefix is present from both protocols.
RIP has a higher metric for that network and metrics always override administrative distance: Metrics are compared only within a single protocol. When choosing between different protocols, administrative distance takes priority.
The RIP path is rejected because it contains a routing loop: The question does not mention any loop conditions, and routing loops are not automatically assumed when multiple protocols advertise the same route.
RIP cannot advertise routes that overlap with EIGRP routes in the same router: A router can receive and store routes from multiple protocols for the same destination. Only one becomes active in the table based on administrative distance and other selection rules.

Common Pitfalls:
Learners often confuse administrative distance with metric values such as hop count or composite metrics. Another common issue is forgetting the default distance values for major protocols, which leads to incorrect assumptions about which protocol will win. To avoid mistakes, memorise the key defaults and remember that administrative distance decides between protocols first, and only after that does the router examine metrics within a single protocol to choose the best route.

Final Answer:
EIGRP has a lower administrative distance than RIP, so it is preferred