Which three reasons would account for this issue? (Choose three.)
Click on the arrows to vote for the correct answer
A. B. C. D. E.ABC
This question appears to be specific to a networking scenario involving the IS-IS protocol and its configuration. Based on the provided answer choices, the issue seems to be related to connectivity problems in the network.
Here are the three possible reasons that could account for this issue, along with their explanations:
A. A lack of or a malformed ISO network entity title (NET) on the loopback interface would cause this issue.
The ISO network entity title (NET) is a unique identifier used in the IS-IS protocol to distinguish different areas and nodes in the network. If the loopback interface, which is a virtual interface used for management and routing purposes, is missing an ISO NET or has a malformed one, it could cause connectivity problems. For example, other nodes in the network may not be able to properly identify or reach the loopback interface due to the missing or malformed ISO NET.
B. The interface MTU might be less than 1492.
MTU stands for Maximum Transmission Unit, which is the largest packet size that can be transmitted over a network. The default MTU size for Ethernet networks is 1500 bytes, but if the network has devices or links that support smaller MTU sizes, such as DSL or PPPoE connections, the MTU may need to be adjusted accordingly. If the interface MTU is less than 1492, it could cause connectivity problems, especially for protocols like IS-IS that require larger packet sizes.
C. The IS-IS protocol on the loopback interface has not been enabled.
IS-IS is a link-state routing protocol used in some networks to exchange routing information and calculate the best path to different destinations. If the IS-IS protocol is not enabled on the loopback interface, other nodes in the network may not be able to exchange routing information with it. This could result in connectivity problems and a lack of reachability to certain destinations in the network.
D. The area IDs might be matched and should be set differently.
In IS-IS, network nodes are organized into areas to simplify routing and reduce the amount of traffic and overhead on the network. Each area has a unique area ID that distinguishes it from other areas in the network. If two areas have the same area ID, it could cause connectivity problems and routing inconsistencies. Therefore, it's important to ensure that area IDs are set correctly and do not overlap.
E. An ISO NET might not be configured on the physical interface.
Similar to reason A, if an ISO NET is not properly configured on the physical interface, it could cause connectivity problems and prevent other nodes from properly identifying or reaching the interface. This could be due to a configuration error or oversight during the initial network setup.
In summary, the three reasons that could account for the connectivity issue in this scenario are: