Route selection by administrative distance: If a routing table contains a static route, a RIP route, and an IGRP route to the same destination network, which route will the router prefer by default?

Introduction / Context:
Routers often learn multiple routes to the same destination from different sources. The tie-breaker among protocols is administrative distance (AD), a trust metric where lower values are preferred. Understanding AD is critical to predicting which path will be installed in the routing table and used for forwarding.

Given Data / Assumptions:

• Three candidates exist: static, RIP, and IGRP.
• All routes point to the same prefix with viable next hops.
• No policy overrides (e.g., floating static with higher AD) are in play.

Concept / Approach:

Default administrative distance values (classic IOS) are: connected 0, static 1, EIGRP summary 5, eBGP 20, IGRP 100, OSPF 110, IS-IS 115, RIP 120. The route with the lowest AD wins and is installed in the routing table. Static routes use AD 1 unless configured otherwise.

Step-by-Step Solution:

Verification / Alternative check:

Run show ip route and observe the installed entry’s code and administrative distance/metric in brackets. Removing the static route should reveal the next-best protocol path (IGRP, then RIP).

Why Other Options Are Wrong:

RIP and IGRP have higher ADs, so they lose to the static route.

Load-balancing occurs only among equal-AD, equal-metric routes; differing AD prevents that.

“Any available route” ignores the deterministic AD selection rule.

Common Pitfalls:

Forgetting that you can raise a static route’s AD (floating static) to act as a backup; confusing protocol metrics with administrative distance—they solve different problems.

Final Answer:

Static route