Networking Routing Believability and Administrative Distance by Anthony Sequeira

If a network is running more than one routing protocol (maybe as a result of a corporate merger), and a router receives two route advertisements from different routing protocols for the same network, which route advertisement does the router believe? Interestingly, some routing protocols are considered to be more believable than others. For example, a Cisco router would consider EIGRP to be more believable than RIP.

The index of believability is called administrative distance (AD). Table 10-1 shows the AD values for various sources of routing information. Note that lower AD values are more believable than higher AD values.

Routing Information Source AD value
Directly connected network 0
Statically configured network 1
OSFP 110
RIP 120
External EIGRP 170
Unknown or unbelievable 255

You can configure a router to prefer RIP routes over IGRP using the distance command as shown below.

R1(config)#router rip R1(config-router)#distance 80

This will configure router R1 with an administrative distance of 80 for RIP protocol.

About The Author

Anthony Sequeira, CCIE No. 15626, is a Cisco Certified Systems Instructor (CCSI) and author regarding all levels and tracks of Cisco Certification. Anthony formally began his career in the information technology industry in 1994 with IBM in Tampa, Florida. He quickly formed his own computer consultancy, Computer Solutions, and then discovered his true passion-teaching and writing about Microsoft and Cisco technologies. Anthony joined Mastering Computers in 1996 and lectured to massive audiences around the world about the latest in computer technologies. Mastering Computers became the revolutionary online training company, KnowledgeNet, and Anthony trained there for many years. Anthony is currently pursuing his second CCIE in the area of Security and is a full-time instructor for the next-generation of KnowledgeNet, Anthony is also a VMware Certified Professional.

CompTIA Network+ N10-008 Cert Guide contains proven study features that allow you to succeed on the exam the first time. Expert instructor Anthony Sequeira shares preparation hints and test-taking tips, helping you identify areas of weakness and improve both your conceptual knowledge and hands-on skills, essential for successful completion of the performance-based testing items on the exam. This complete, CompTIA-approved study package includes the following:

A test-preparation routine proven to help you pass the exams
Clearly defined chapter learning objectives covering all N10-008 exam topics
Chapter-ending review questions and exam preparation exercises, which help you drill on key concepts you must know thoroughly
The powerful Pearson Test Prep practice test software, complete with hundreds of well-reviewed, exam-realistic questions, customization options, and detailed performance reports
40 performance-based exercises to help you prepare for the hands-on exam questions
A free copy of the CompTIA Network+ N10-008 Simulator Lite software, complete with meaningful lab exercises that enhance your hands-on skills
More than 60 minutes of video mentoring
A final preparation chapter that guides you through tools and resources to help you craft your review and test taking strategies
An Exam Essentials appendix that quickly recaps all major chapter topics for easy reference, both in print and interactive digital format
A key terms Glossary in both print and on the companion website, which acts as an interactive flash-card application
Study plan suggestions and templates to help you organize and optimize your study time
A 10% exam discount voucher (a $33+ value!)

Well regarded for its level of detail, study plans, assessment features, challenging review questions and exercises, video instruction, and hands-on labs, this approved study guide helps you master the concepts and techniques that ensure your exam success.

Master the topics on the CompTIA Network+ N10-008 exam, including:

Network topologies and media types
IP addressing
Network services
Data center architectures and cloud concepts
Routing, Ethernet switching, and wireless networking
Network availability and disaster recovery
Network security
Remote access
Network troubleshooting

Reader Paulo Cardoso says, "This is a great book. In addition, it comes with great additional resources."

Learn more about the CompTIA Network+ N10-008 Cert Guide at

Learn more at

More Networking Protocols and Standards:
• PoE (Power Over Ethernet)
• Routing Datagrams
• X.25 and Frame Relay Overview
• IPv6 Global Unicast Addresses
• The OSI Reference Model
• SYN-ACK Handshake to Establish a TCP Connection
• Neighbor Discovery Protocol (NDP)
• Video Streaming Protocols
• Network Operating Systems
• IPv6 Prefix Length Notation