EIGRP Cost Calculation Problem
Scenario:
Imagine you are the network administrator for a company with a simple network consisting of three routers: Router A, Router B, and Router C. These routers are interconnected using Ethernet links. The routers are configured to use EIGRP (Enhanced Interior Gateway Routing Protocol) for routing.
### Network Topology
- Router A:
- LAN Interface: 192.168.1.1/24
- WAN Interface to Router B: 10.1.1.1/30
- WAN Interface to Router C: 10.1.2.1/30
- Router B:
- LAN Interface: 192.168.2.1/24
- WAN Interface to Router A: 10.1.1.2/30
- WAN Interface to Router C: 10.1.3.1/30
- Router C:
- LAN Interface: 192.168.3.1/24
- WAN Interface to Router A: 10.1.2.2/30
- WAN Interface to Router B: 10.1.3.2/30
### Link Details
- Link A-B:
- Bandwidth: 100 Mbps
- Delay: 1000 microseconds
- Link A-C:
- Bandwidth: 100 Mbps
- Delay: 500 microseconds
- Link B-C:
- Bandwidth: 50 Mbps
- Delay: 1500 microseconds
### EIGRP Cost Calculation Formula
EIGRP uses a composite metric that considers bandwidth and delay by default. The formula for EIGRP metric calculation is as follows:
\[ \text{Metric} = \left( \frac{10^7}{\text{minimum bandwidth}} \right) + \left( \frac{\text{sum of delays}}{10} \right) \times 256 \]
Where:
- Bandwidth is in kilobits per second (Kbps).
- Delay is in microseconds.
- The metric is multiplied by 256 to produce the final metric.
### Exercises
Exercise 1:
Calculate the EIGRP metric from Router A to Router B over the direct link.
Exercise 2:
Calculate the EIGRP metric from Router A to Router C over the direct link.
Exercise 3:
Calculate the EIGRP metric from Router B to Router C over the direct link.
Exercise 4:
Calculate the EIGRP metric from Router A to Router C through Router B.
Exercise 5:
If Router C has two paths to Router A, one direct and one via Router B, which path will it prefer based on EIGRP metrics?
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1August 23, 2024 355
