Final answer:
The default administrative distance for eBGP routes is 20, which is a key factor used by routers to select the best path for network traffic.
Step-by-step explanation:
The default administrative distance of an eBGP (External Border Gateway Protocol) route is 20. Administrative distance is a measure used by routers to choose the best path when there are two or more different routes to the same destination from two different routing protocols.
The options listed in the question are incorrect as the administrative distances for eBGP and other routing protocols are defined by default values in networking devices such as routers. For instance, eBGP has a default administrative distance of 20, which is not listed among the options provided (90, 100, 110, 120). These values can be very important for network engineers and administrators when setting up and troubleshooting network routing policies to ensure that the most reliable routes are chosen.