RIP or the Routing Information Protocol was standardized in RFC1058 in 1988. It was developed from earlier routing protocols developed at Xerox. RIP has three major versions RIPv1 (1988), RIPv2 (RFC2453 1998), and RIPng (RFC2080 1997). RIP version 2 added support for VLSM and CIDR and version ng or next generation adds support for IPv6. 

RIPv1 Characteristics

1. Classful routing – RIP is a classful routing protocol, it does not send or receive subnet masks, it assumes classful subnet masks

2. Periodic updates – RIP broadcasts routing updates every 30 seconds. It broadcasts the entire routing table in the update.

3. Triggered updates – RIP also broadcasts updates when there is a change in the topology, like a network going up or down.

4. Metric – RIP’s metric is hop count. A hop is a router, so a RIP route with metric of 2 means the network is two routers away. RIP’s maximum distance is 15 hops. 16 hops is infinity and is used to mark a route as dead. A router that receives a packet  then removed from the routing table. 

5. Administrative Distance – RIP’s administrative distance is 120. AD ranks the trustworthiness, or reliability of the route, the lower the administrative distance the better the route.

6. Hold Down Timer – RIP uses a hold down timer of 180 seconds so that it does not propagate bad routes and does not have a count-to-infinity routing loop. Route is flushed at 240 seconds

7. Load Balancing – Default load balancing across 4 equal cost routes. Can go up to 6 routes.

8. Count to infinity – is prevented by hold down timers and by RIPs maximum metric of 15 hops.

9. Routing Loops – are prevented by: Hold Down Timer, Split Horizon Rule, Route Poisoning, Route Poisoning with Poison Reverse, as well as TTL.

10. Automatic Route Summarization. RIP automatically summarizes routes into classful network ranges because it will not allow non-classful network configuration or the propagation of non-classful subnet masks. It can only advertise classful networks. This can cause problems if subnetted networks are configured on multiple router interfaces in a discontiguous manner (see the video tutorials below for a demonstration).

11. Transport Layer – RIP sends out updates on UDP port 520

IOS CLI commands to use with RIP

router(config)#router rip //to activate RIP
router(config-router)#network <network ip address>
//to add a participating network and interface
router(config-router)#passive-interface <interface type> <interface number> //
to stop RIP from sending updates out of an interface
router#show running-config
//to verify your configuration
router#show ip route
//to verify your routing table
router#show ip protocols
//to verify your RIP configuration
router#copy running-config startup-config
//to save your configuration

 Video Tutorials

In this part, I prepare the network and configure the network interfaces

In this part, I demonstrate how RIP auto-summarizes classless subnets

In this part, I demonstrate how auto-summary can create a problem if the networks are discontiguous

Dynamic Routing Protocols


With complex networks, hierarchically designed networks, networks with redundancy, or networks requiring more than two routers it is often beneficial to use a dynamic routing protocol instead of using only static routes.

Dynamic Routing Protocols

Distance Vector versus Link State


Various routing protocols and their characteristics

Static and Default Routes


It is important to know how to configure static routes on a router. Many networks are small enough that all of the routing can be handled by a few static routes and a default route out of the network. If you want to know a router’s routes you need to look at its routing table. The routing table will show you connected routes, static routes, if there is a default route, and it will also show you if there are any dynamically learned routes too. In this section we will look at connected routes, static routes and default routes.

Connected Routes

Connected routes are routes to networks directly connected to the router. To establish connected routes all you have to do is bring up your router’s interfaces. This means configuring the router’s interfaces with IP addresses and subnet masks and making sure they are not in an administratively shutdown state.

To configure a Fast Ethernet interface from global configuration mode:

R1(config)#interface fastethernet 0/0
R1(config-if)#ip address <your ip address> <your subnet mask>
R1(config-if)#description <your description>
R1(config-if)#no shutdown

To configure a serial interface from global configuration mode. You can first check to see if your interface is the DCE and will need a clock rate:

R1#show controllers serial 0/0

Checking the “show controllers” command results to see If the interface is the DCE, you can see from the output below, that the interface is in fact the DCE, and that the clock rate needs to be set.


R1(config)#interface serial 0/0
R1(config-if)#ip address <your ip address> <your subnet mask>
R1(config-if)#clock rate 64000 (only if the interface is the DCE)
R1(config-if)#description <your description>
R1(config-if)#no shutdown

Now that the interfaces have been brought up you can see the connected routes by looking at the routing table by issuing a “show ip route” command and looking for the lines that start with “c”:

Static Routes

In the picture below, R1 has three connected networks in its routing table but it does not know about the network and therefore cannot route traffic to it. To solve that problem a static route to the network can be configured.

There are two ways of configuring a static route. The first uses the next hop router’s IP address on the connected network:
     R1(config)#ip route <destination network> <subnet mask> <next hop router address>

The second uses the router’s own exit interface. This way is faster for the router because it doesn’t have to first look up the exit interface from the connected network:

R1(config)#ip route <destination network> <subnet mask> <local router exit interface> 

both types of static route commands are listed below:


After the static route has been configured you should be able to verify the static route in the router’s routing table be issuing a #show ip route command and looking for the “s” entry in the routing table. The image below shows the router’s routing table after a static route was configured and the “show ip route” command was executed. Notice the highlighted static route which starts with an “s” in the routing table:
     R1(config)#ip route fa1/0
R1#show ip route

Default Routes

In the diagram below R1 needs a default route or gateway of last resort configured so that it can route traffic to unknown networks across the internet. If R1 does not have a default route, traffic to all unknown networks will be dropped, and surfing the Web will not be possible. To configure a default route you must configure a static route to the network and subnet mask to the next hop router or exit interface which has a path out of the network (see below). The commands to create a default route or gateway of last resort are:

R1(config)#ip route <next hop router IP address>
R1(config)#ip route <exit interface>

Once you have configured a default route it will show up in the routing table as an “s” with an asterisk “*” next to it signifying it as a default route. You can also see from the highlighted areas in the routing table output below that the default route is also acknowledged as the “Gateway of last resort is to network” (see below):

Video Tutorial on Default Routes

In this video I demonstrate configuring a default route using Packet Tracer

Subnetting Challenge

Subnetting Network Challenge

Look at the network diagram below, fill in the correct IP addresses based on the information given in the diagram, and click the “Check Your Answer” button to check your answer. Fill in the fields with IP addresses and no subnet masks, the correct subnet masks are assumed.

Note: The diagram above relates to a PT Skills Challenge in the Cisco Routing Protocols and Concepts Curriculum (section 1.5.3 – 2) This visual diagram may help you make sense of that particular Packet Tracer as well as practice your subnetting skills.

Welcome to Cisco CCNA 2

CCNA 2 Introduction

The Cisco CCNA certification is the most well known computer networking certification in the industry. I recommend a Cisco course of study and the Cisco Academy Curriculum in particular to anyone who wants to learn about computer networking. It is the best foundation to teach how networks communicate, the protocols that are involved, the network addressing, subnetting, routing, switching, VLANs and more!

As a Cisco Networking Academy instructor I have taught the Cisco CCNA curriculum for over 12 years. The Cisco Academy offers 4 classes that together map to the Cisco CCNA certification exam. The current exam is the 200-120 CCNA, which has a stronger emphasis on IPv6. All students that are enrolled through the college will qualify to be enrolled in the Cisco Academy, and all Cisco Academy students will have access to online curriculum materials as well as the latest version of Packet Tracer (6.1), a great tool for creating simulated networked environments, complete with functioning routers, switches, and hosts.

In fall 2013, the Cisco Academy released an updated version of their CCNA curriculum. This updated curriculum coincides with the new 200-120 CCNA exam and includes many new area of study including a much stronger empahasis on IPv6.

Course Materials

All of the course materials are available through the Cisco Academy website through their learning management system. This includes the complete text, the Packet Tracer software program, interactive activities, multiple choice exams, and plenty of labs with complete instructions. If you prefer a paper copy of the text you can purchase one online from Cisco Press or Amazon. Make sure you order a current version of the text. I have provided a link to the text at Cisco Press and the ISBN number:

Routing and Switching Essentials Companion Guide
: ISBN: 1587132060 / ISBN 13: 9781587132063

Class Availability

  • How can I enroll in a class?
    I teach the Cisco CCNA through Central Oregon Community College. To sign up for the class and attend remotely online, look for new student registration at
  • Where can I do my labs?.
    Some labs will be done in class, some labs will be done at home using Packet Tracer, and some labs can be done by remotely by connecting to the CIS Department Netlab+ server.
  • What if I am an online student, and I can’t come to the lab?
    If you are an online student, I recommend that you login to Blackboard and attend the class online through the Blackboard video conferencing tool. The is always available through video conference and it will also be recorded and available for watching later.
  • How will I turn in assignments?
    Exams will be taken online through the Cisco Academy website and learning management system. Labs will be turned into me directly.
  • What are the assignments and how will I be graded?
    I grade on a point system. Every week you will have the opportunity to
    earn points from chapter exams and chapter labs. At the end of the class there is a cumulative multiple choice final exam and a cumulative lab final.

Routers and Routing Intro


Some of the ideas that are covered in this section are how Cisco routers are put together, their different types of memory, their various interfaces both LAN and WAN, and their start-up processes? Allso in this section there is a review on how to configure a router, how to bring up its interfaces, and how to issue show commands to read its status. This first part of CCNA 2 also covers in an introductory way the router’s routing table, and static versus dynamic routing.

Router Memory

Similar yet different from a regular computer, the router has different kinds of memory ROM, Flash, NVRAM, and SDRAM which all have different functions:

  • ROM – POST, Bootstrap, and ROMMON
  • Flash – IOS
  • NVRAM – Configuration File
  • SDRAM – Running-Config, Routing Table, IOS (everything is loaded and executed from RAM)

Notice: The router is a computer but it does not have a traditional hard drive to store files and the operating system, this is accomplished in Flash memory and NVRAM memory.

Bootup Process

  1. POSTROM memory,
  2. BootstrapROM memory,
  3. Load the IOS – the router has an ordered routine for loading the IOS

    1. Flash Memory – the IOS is typically loaded from Flash memory
    2. TFTP – if there is no IOS in Flash, the router will search for a network TFTP server,
    3. ROM – if there is no IOS found, the router defaults to a recovery IOS called Rommon,
  4. Load the Startup-Configthe router has an ordered routine for loading the startup-config file

    1. NVRAM memory – the startup-config file is typically loaded from NVRAM memory
    2. TFTP – if there is no config file in NVRAM, the router will search for a network TFTP server,
    3. Setup-Mode – if there is no configuration file found, the router defaults to setup-mode

The Function of the Router

The router’s purpose or function is to find the best path (route) and switch out of the correct interface. The router will make the decision of the “best path” by first determining the destination network, and second by consulting its routing table.

Static Routing and Dynamic Routing

Routers can be configured to route traffic based on static routes that have to be manually entered by an administrator or by dynamic routes that are created dynamically by a routing protocol. Static routing is a good choice for networks that: never change, are small in size or have only one router, or have only one way out of the network. Dynamic routing is a good choice if a network has multiple routers, is part of a larger network, or if the network changes frequently. For instance, in a situation where the network changes, with a dynamic routing protocol if a network goes down, the routers will inform each other automatically through the routing protocol, and the route will be removed from the routing table; with static routing, if a network goes down, an administrator will have to go in and remove the the static route manually.

There is a difference between routed or routable protocols and routing protocols. A routed protocol is a protocol that is routable over multiple networks like the internet. Today the de facto routed protocol is TCP/IP. A routing protocol is a protocol used by routers to share information with each other, specifically information about available routes. Examples of routing protocols would be RIP, EIGRP, OSPF, and ISIS.

For the Cisco CCNA certification exam you will need to know how to configure an interior gateway routing protocol in a multiple router network. You will be required to know the following interior gateway routing protocols: RIPv1, RIPv2, EIGRP, and OSPF.

Routed Protocols
IPX/SPX (Novell – no longer in use)
Apple Talk (Apple – no longer in use)

 Routing Protocols

RIP v1 – interior gateway protocol, IETF – RFC1058, open standard
RIP v2 – interior gateway protocol, IETF, open standard
EIGRP – interior gateway protocol, Cisco proprietary
OSPF – interior gateway protocol, IETF, open standard
ISIS – interior gateway protocol, covered in CCNP
BGP – exterior gateway protocol, covered in CCNP

Interior Gateway Routing Protocol Types
Distance Vector     Link State  

The Routing Table and RIP

A demonstration of reading routing tables and activating the RIP routing protocol 



In the tutorials below, I configure DHCP and NAT and demonstrate its function using Packet Tracer.

Video Tutorials

Configure the Cisco router to function as a DHCP server

Configure the Cisco router to relay DHCP requests to the DHCP server using an ip helper-address

Configure the router as a DHCP relay agent – Take 2

Network Address Translation (NAT) – Part 1

Network Address Translation (NAT) – Part2

Network Address Translation (NAT) – Part3

Network Address Translation (NAT) – Part4