# Day 25: RIP and EIGRP Routing Protocols

# CCNA Study Guide: Comparative Analysis of RIP and EIGRP

## 1.0 Introduction

While OSPFv2 is the primary protocol for configuration on the CCNA 200-301 exam, understanding RIP and EIGRP is essential for mastering routing fundamentals. These protocols represent the evolution of distance-vector logic and provide context for why modern networks are designed the way they are.

## 2.0 Routing Information Protocol (RIP)

RIP is the classic "Routing by Rumor" protocol. It is a legacy Interior Gateway Protocol (IGP) that relies on periodic updates and a simplistic view of the network.

### 2.1 Core Characteristics

- Algorithm: Bellman-Ford (Distance Vector).
- Metric: Hop Count. Each router is one hop; the path with the fewest routers is chosen.
- Maximum Hop Count: 15. A hop count of 16 is considered "infinite" (unreachable).
- Administrative Distance (AD): 120.
- Update Timer: Full routing table broadcast/multicast every 30 seconds.

### 2.2 Evolution: RIPv1 vs. RIPv2

RIP evolved to support modern networking requirements like VLSM and CIDR.

<div align="left" dir="ltr" id="bkmrk-feature-ripv1-ripv2-"><table><colgroup><col width="131"></col><col width="245"></col><col width="193"></col></colgroup><tbody><tr><td>Feature

</td><td>RIPv1

</td><td>RIPv2

</td></tr><tr><td>Addressing

</td><td>Classful (A, B, C)

</td><td>Classless (VLSM/CIDR)

</td></tr><tr><td>Subnet Masks

</td><td>Not sent in updates

</td><td>Included in updates

</td></tr><tr><td>Transmission

</td><td>Broadcast (255.255.255.255)

</td><td>Multicast (224.0.0.9)

</td></tr><tr><td>Authentication

</td><td>Not supported

</td><td>Supported

</td></tr></tbody></table>

</div>### 2.3 Basic Configuration

Router(config)# router rip

Router(config-router)# version 2

Router(config-router)# no auto-summary

Router(config-router)# network 192.168.1.0

Router(config-router)# passive-interface g0/0

Router(config-router)# default-information originate

## 3.0 Enhanced Interior Gateway Routing Protocol (EIGRP)

EIGRP is an Advanced Distance Vector (or Hybrid) protocol. It is designed for extremely fast convergence and efficiency, utilizing the Diffusing Update Algorithm (DUAL).

### 3.1 Core Characteristics

- Algorithm: DUAL.
- Multicast Address: 224.0.0.10.
- Administrative Distance (AD): 90 (Internal), 170 (External).
- Convergence: Very fast due to pre-calculated backup paths.
- Routing Code: Identified in the routing table by the letter D (for DUAL).

### 3.2 The Composite Metric

EIGRP uses a complex formula considering multiple path attributes. By default, only Bandwidth and Delay are used.

$$Metric = (\[Slowest\\ Bandwidth + Sum\\ of\\ Delays\] \\times 256)$$

### 3.3 EIGRP Terminology (DUAL)

<div align="left" dir="ltr" id="bkmrk-term-definition-succ"><table><colgroup><col width="188"></col><col width="417"></col></colgroup><tbody><tr><td>Term

</td><td>Definition

</td></tr><tr><td>Successor

</td><td>The best, lowest-metric route installed in the routing table.

</td></tr><tr><td>Feasible Successor (FS)

</td><td>A loop-free backup route.

</td></tr><tr><td>Feasible Distance (FD)

</td><td>The local router's total metric to the destination.

</td></tr><tr><td>Reported Distance (RD)

</td><td>The metric advertised by a neighbor to reach the destination.

</td></tr></tbody></table>

</div>The Feasibility Condition: For a neighbor to be a Feasible Successor, its RD must be less than the current FD ($RD &lt; FD$). This ensures a loop-free backup path.

## 4.0 Advanced Features and Configuration

### 4.1 Unequal-Cost Load Balancing

EIGRP is the only IGP that supports unequal-cost load balancing. Using the variance command, a router can distribute traffic across paths with different metrics if the backup path is a Feasible Successor.

### 4.2 Configuration Example

Router(config)# router eigrp 100

Router(config-router)# eigrp router-id 1.1.1.1

Router(config-router)# network 10.0.0.0 0.0.0.255

Router(config-router)# no auto-summary

Router(config-router)# variance 2

## 5.0 Verification and Troubleshooting Commands

<div align="left" dir="ltr" id="bkmrk-command-purpose-show"><table><colgroup><col width="193"></col><col width="411"></col></colgroup><tbody><tr><td>Command

</td><td>Purpose

</td></tr><tr><td>show ip protocols

</td><td>Summarizes all active routing protocols (timers, AD, networks).

</td></tr><tr><td>show ip route \[rip | eigrp\]

</td><td>Filters the routing table for specific protocol entries.

</td></tr><tr><td>show ip eigrp neighbors

</td><td>Verifies successful adjacencies with neighboring routers.

</td></tr><tr><td>show ip eigrp topology

</td><td>Displays the DUAL database, including Successors and FS.

</td></tr></tbody></table>

</div>## 6.0 Head-to-Head Comparison: RIP vs. EIGRP

<div align="left" dir="ltr" id="bkmrk-feature-rip-eigrp-ty"><table><colgroup><col width="139"></col><col width="151"></col><col width="212"></col></colgroup><tbody><tr><td>Feature

</td><td>RIP

</td><td>EIGRP

</td></tr><tr><td>Type

</td><td>Distance Vector

</td><td>Advanced Distance Vector

</td></tr><tr><td>Metric

</td><td>Hop Count

</td><td>Bandwidth + Delay

</td></tr><tr><td>Convergence

</td><td>Slow

</td><td>Very Fast

</td></tr><tr><td>Load Balancing

</td><td>Equal Cost Only

</td><td>Equal &amp; Unequal Cost

</td></tr><tr><td>Admin Distance

</td><td>120

</td><td>90

</td></tr><tr><td>Standard

</td><td>Industry Standard

</td><td>Cisco (Open since 2013)

</td></tr></tbody></table>

</div>