Which routing protocol has the highest administrative distance (AD) of the following?

The routing protocol with the highest administrative distance among the listed options is iBGP (Internal Border Gateway Protocol). Administrative distance is a value used by routers to rank the trustworthiness of different routing protocols. When a router learns about multiple routes to the same destination from different protocols, it will choose the one with the lowest administrative distance.

In this case, iBGP has a higher administrative distance compared to the other protocols listed: RIP, EIGRP, and IS-IS. Specifically, iBGP has an administrative distance of 200. In contrast, RIP has an administrative distance of 120, EIGRP has 90, and IS-IS has a typical distance of 115.

This higher AD means that routes learned via iBGP are less preferred than those from other routing protocols with lower administrative distances, which affects route selection in the presence of multiple routing protocols. Understanding the concept of administrative distance is crucial for network design and troubleshooting, as it helps determine which routes are utilized in the routing table.