mediumMultiple Choice
350-401 Practice Question: An engineer is troubleshooting an EIGRP…
An engineer is troubleshooting an EIGRP convergence issue in a network with redundant links. The engineer notices that when a primary link fails, the backup link takes over immediately, but the routing table shows the route with a higher metric. The engineer wants to ensure that the backup link is used only when the primary fails, and that traffic is not load-balanced. The engineer has configured 'variance 2' on all routers. What is the most likely effect of this configuration?
⚠ Common exam trap
Cisco often tests the misconception that 'variance' only affects feasible successor selection or that it is used for equal-cost load balancing, when in fact it directly controls the installation of multiple unequal-cost paths into the routing table.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The variance 2 command causes EIGRP to install both the primary and backup routes, resulting in unequal-cost load balancing.
The 'variance 2' command in EIGRP allows the router to install multiple routes to the same destination network in the routing table, even if their metrics are not equal, as long as the metric of the alternate route is within the variance multiplier (2x) of the best metric (the feasible distance). Since the backup link has a higher metric but is within the variance, EIGRP installs both routes, causing unequal-cost load balancing. This explains why the backup link is actively used for traffic, contrary to the engineer's desire to use it only as a failover.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The variance 2 command causes EIGRP to install only the best metric route, so the backup link is not used.
Why it's wrong here
Variance 2 actually broadens which EIGRP routes are installed, not narrows it. It multiplies the successor's feasible distance by 2 and admits any feasible successor whose metric is at or below that product, so a lower-bandwidth backup path can enter the routing table. The only way to keep a backup link unused is to leave variance at 1 (default) or to use an offset-list to raise the backup's metric above the multiplier threshold.
- ✓
The variance 2 command causes EIGRP to install both the primary and backup routes, resulting in unequal-cost load balancing.
Why this is correct
With variance 2, the primary route's feasible distance is doubled, so any feasible successor whose composite metric falls within twice that value is installed alongside the primary. This installs both routes and enables unequal-cost load balancing, meaning packets are distributed across the two links in proportion to the inverse of their metrics. For an engineer who wants the primary link to carry 100% of traffic unless it fails, this variance setting is counterproductive because the backup link will be actively used, which is exactly the unintended behavior described.
- ✗
The variance 2 command has no effect on route installation; it only affects the feasible successor selection.
Why it's wrong here
Variance directly controls which routes are placed into the IP routing table, not just which neighbors are feasible successors. Feasible-successor selection depends on the feasibility condition, comparing the next-hop's reported distance to the current feasible distance, and that happens even when variance is at its default of 1. Variance is applied after that selection, as a multiplier to decide which already-feasible candidates exceed the metric threshold and thus get installed in the RIB. Without variance, only the successor (best path) is installed; with a higher variance, additional feasible successors are installed.
- ✗
The variance 2 command is used for equal-cost load balancing only.
Why it's wrong here
Variance is specifically designed for unequal-cost load balancing; equal-cost load balancing is automatic in EIGRP whenever multiple feasible successors have identical metrics and does not require any variance configuration. If variance only handled equal-cost paths, it would be redundant because EIGRP already installs and load-balances across equal-metric routes by default. Variance extends that capability to paths whose metrics differ, for example a 100 Mb/s link and a 10 Mb/s link, by admitting the higher-metric route as long as its metric is less than or equal to variance multiplied by the best metric.
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
About these practice questions
One of 1,923 original 350-401 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.