EIGRP Metric Calculation – Understand the Brain Behind Route Selection. [CCNP ENTERPRISE]

We often configure EIGRP and move on, but do we ever pause and ask — how does EIGRP decide which path is the best? The answer lies in its metric calculation — the “math” behind routing decisions.

Trust me, once you understand EIGRP’s metric logic, you’ll troubleshoot smarter, design better, and even pass your certifications with confidence. Let’s keep it hands-on and practical as always.

---

Theory in Brief – What is EIGRP Metric?

EIGRP (Enhanced Interior Gateway Routing Protocol) is a Cisco-proprietary, advanced distance-vector routing protocol. It’s considered a hybrid because it uses some link-state behavior like DUAL (Diffusing Update Algorithm) and supports fast convergence.

But what really powers EIGRP is its metric calculation, which determines the “best” route to a destination.

---

Default EIGRP Metric Formula

EIGRP uses this formula to calculate the metric:

Metric = 256 × ((10⁷ / min bandwidth in kbps) + cumulative delay in tens of microseconds)

That’s the default metric when only bandwidth and delay are considered. Reliability and Load are optional and disabled by default.

---

Components of the Metric:

• Bandwidth – Minimum bandwidth of the path
• Delay – Cumulative delay across the entire path
• Reliability – Optional; based on interface reliability
• Load – Optional; based on traffic load
• MTU – Not used in metric but propagated

EIGRP allows fine control using K-values (K1 to K5). By default:

• K1 = 1 (Bandwidth)
• K3 = 1 (Delay)
• Others = 0

This means only bandwidth and delay are factored in by default.

---

Example

If a path has:

• Bandwidth = 1000 kbps
• Delay = 20000 microseconds

Then:

• Metric = 256 × ((10⁷ / 1000) + 2000) = 256 × (10000 + 2000) = 3,072,000

This number is what EIGRP uses to compare routes. Lower metric = better route.

---

Key Parameters

Parameter	Used in Metric?	Description	Default in Calculation
Bandwidth	Yes	Slowest link in kbps	K1 = 1
Delay	Yes	Total delay across all hops (μs/10)	K3 = 1
Reliability	Optional	Measure of link stability (1–255)	K2 = 0
Load	Optional	Dynamic interface traffic	K4/K5 = 0
MTU	Not used	Propagated but not metric-influencing	–

---

Pros and Cons of EIGRP Metric System

Pros	Cons
Intelligent path selection based on real values	Complex formula for beginners
Allows fine-tuning using K-values	Changing K-values must match on all routers
Fast convergence using DUAL algorithm	Cisco proprietary (less cross-vendor support)
Supports unequal-cost load balancing (variance)	Metric may not reflect real-time traffic conditions

---

Essential CLI Commands

Command	Purpose
show ip eigrp topology	View route metrics and topology info
show ip route eigrp	Check EIGRP entries in routing table
show ip eigrp interfaces	Show interfaces participating in EIGRP
show ip protocols	View K-values and routing info
show running-config	Confirm bandwidth, delay settings
interface x/x delay 1000	Adjust delay on interface
bandwidth 1000	Change bandwidth to influence metric
router eigrp 100 variance 2	Enable unequal-cost load balancing

---

Real-World Use Case

Scenario	How EIGRP Metric Helps
Branch office connected via MPLS and broadband	EIGRP chooses MPLS due to better delay/bandwidth
Data center links with different speeds	Ensures primary path goes via 10G instead of 1G
ISP failover with floating static + EIGRP	EIGRP adapts routes, static kicks in if EIGRP fails
Unequal link paths (10 Mbps vs 100 Mbps)	Use variance to utilize both paths smartly
Wireless vs Wired WAN paths	Delay/bandwidth helps prioritize reliable wired paths

---

EVE-NG LAB – See the Metric in Action

Topology

• R1 connects to R3 via R2 and R4 (different delays/bandwidths)
• EIGRP running on all routers

---

Configuration Snippet

On All Routers:

router eigrp 100
 network 192.168.0.0

On Interfaces (to simulate metric difference):

interface g0/1
 bandwidth 1000
 delay 100

interface g0/2
 bandwidth 100
 delay 1000

Use:

show ip eigrp topology

…to observe differences in feasible distance.

---

Test:

• Ping from R1 to R3
• Shut one path, observe route change
• Use variance 2 on R1 to enable unequal load balancing

---

Troubleshooting Tips

Symptom	Cause	Solution
EIGRP not choosing preferred path	Delay/Bandwidth imbalance	Tune interface metrics
No EIGRP neighbor	K-values mismatch or ACL	Use show ip protocols, check configs
High metric shown unexpectedly	Wrong interface delay/bandwidth	Use show interface, adjust values
Unequal paths not used	Variance not set	Use variance under router config
Route not appearing in RIB	Feasibility condition not met	Check AD and FD, adjust metrics if needed

---

Frequently Asked Questions (FAQs)

1. What is EIGRP metric, and why is it important in route selection?

Answer:
EIGRP (Enhanced Interior Gateway Routing Protocol) uses a composite metric to determine the best path to a destination. This metric is calculated using several parameters such as bandwidth, delay, load, and reliability. Among these, bandwidth and delay are used by default. The lower the metric, the better the route. This calculation helps EIGRP intelligently choose the most optimal path, ensuring efficient and loop-free routing in enterprise networks.

---

2. What are the default K-values used in EIGRP metric calculation?

Answer:
EIGRP uses a formula with K-values (constants) to determine how different parameters influence the metric. The default K-values are:

• K1 = 1 (Bandwidth)
• K2 = 0 (Load)
• K3 = 1 (Delay)
• K4 = 0 (Reliability)
• K5 = 0 (Reliability)

With these defaults, only bandwidth and delay are factored into metric calculation, making it simpler and more stable.

---

3. What is the EIGRP metric formula with default K-values?

Answer:
With default K-values (K1=1, K3=1, others = 0), the metric formula becomes:

Metric = [(10^7 / Minimum Bandwidth in kbps) + Sum of Delays in tens of microseconds] * 256

This means EIGRP prefers higher bandwidth and lower cumulative delay when selecting routes.

---

4. How is bandwidth used in EIGRP metric calculation?

Answer:
EIGRP uses the minimum bandwidth along the path from source to destination. It converts this to a metric by using the formula 10^7 / bandwidth in kbps. Lower bandwidth increases the metric value, making the path less preferred. For instance, a 100 Mbps link gives a better (lower) metric than a 10 Mbps link.

---

5. How is delay calculated and included in the metric?

Answer:
EIGRP adds the cumulative delay of all outgoing interfaces along the path. Delay is measured in microseconds but converted to tens of microseconds for metric calculation. For example, a delay of 10000 microseconds becomes 100. This total delay is added to the bandwidth part before multiplying the result by 256.

---

6. Can load and reliability affect the EIGRP metric?

Answer:
Technically, yes – EIGRP supports load and reliability as metric components. However, since their K-values (K2, K4, and K5) are set to 0 by default, they are not included in the calculation. If these values are manually changed, they can influence route selection, but doing so may introduce instability and complexity in the network.

---

7. How do I view the EIGRP metric values on a Cisco router?

Answer:
Use the following CLI command:

show ip route eigrp

Or to view detailed metric components per route:

show ip eigrp topology

This command shows the feasible distance (FD), bandwidth, delay, reliability, and load for each route in the EIGRP topology table.

---

8. Can I change the delay or bandwidth manually to influence EIGRP metrics?

Answer:
Yes. You can manipulate interface delay and bandwidth to influence EIGRP’s route selection without modifying K-values. For example:

interface GigabitEthernet0/0
 bandwidth 10000
 delay 100

This is commonly used in enterprise networks for traffic engineering or policy-based routing behavior.

---

9. What is the feasible distance and how is it related to metric calculation?

Answer:
The feasible distance (FD) is the total metric from the local router to the destination network via a particular path. It is calculated using the EIGRP metric formula. The FD is stored in the EIGRP topology table and is used to determine the best route. The lowest FD becomes the successor (primary route).

---

10. Is it recommended to change the K-values in EIGRP?

Answer:
In most cases, no. Changing K-values can lead to inconsistent metrics across routers, causing instability or routing loops if not done properly on all EIGRP routers. It’s best practice to leave K-values at their defaults (K1=1, K3=1, others=0) and instead tweak bandwidth or delay per interface if you need to influence routing behavior.

---

YouTube Link

Watch the Complete CCNP Enterprise: EIGRP Metric Calculation – Understand the Brain Behind Route Selection Lab Demo & Explanation on our channel:

---

Final Thoughts

EIGRP’s metric may seem complex at first, but once you understand the logic, you gain predictable control over your network behavior. You’ll no longer be confused why one route is chosen over another — because now you can calculate and influence it.

As always, don’t just read — build this lab in EVE-NG, break things, and learn how to fix them. That’s how real engineers grow.

---

Final Note

Understanding how to differentiate and implement EIGRP Metric Calculation – Understand the Brain Behind Route Selection is critical for anyone pursuing CCNP Enterprise (ENCOR) certification or working in enterprise network roles. Use this guide in your practice labs, real-world projects, and interviews to show a solid grasp of architectural planning and CLI-level configuration skills.

If you found this article helpful and want to take your skills to the next level, I invite you to join my Instructor-Led Weekend Batch for:

CCNP Enterprise to CCIE Enterprise – Covering ENCOR, ENARSI, SD-WAN, and more!

Get hands-on labs, real-world projects, and industry-grade training that strengthens your Routing & Switching foundations while preparing you for advanced certifications and job roles.

Email: info@networkjourney.com
WhatsApp / Call: +91 97395 21088

Upskill now and future-proof your networking career!

---