Available from BrightTools, Activeworx Security Center includes new features for meeting SOX and HIPAA compliance requirements, improved tools for forensic investigation, and much more.

eBusiness Help
Free Trial: Website and Network Monitoring
Avoid The Economic Impact of System Downtimes
Free Trial: Access your files and network from anywhere in the world
Use WebEx PCNow free for 30 days
Free Demo: Increase Your Conversion and Sales
Deliver your message with speaking, animated characters

WebProWorld Networking Forum

Reliable Host?
I am sick of GoDaddy.com. They will not allow off-site MySQL administration and do not allow modifications to the .htaccess file.

What is a good hardware firewall?
I am running my own server in house, using linux. I need a good hardware firewall. I know Symantec used to make a really cool firewall /vpn appliance, but I can seem to find it anymore.

Windows Server 2003 Active Directory/DNS/DHCP
This is going to sound rather strange, but I've got a client who has an "old" Windows Server 2003 on its last legs (one SCSI hard drive is dead, and the other dying in a RAID 1), and what I'd like to be able to do is use the settings for it on the replacement server, which just came in on Monday.



Recent Articles

Passing The CCNA and CCNP: Home Lab Shopping On Ebay
Whether you're just getting ideas for your Cisco home lab or adding to your existing lab, ebay is a great place to get ideas for your lab as well as pick up some great bargains. Of course, the internet being what it is ...

Cisco CCNA / CCNP Tutorial: Home Lab Assembly Case Study
Part of your CCNA / CCNP education is deciding what network topology to use when you're putting together your home lab. Some of you are starting with one or two routers or switches, while others are starting with more.

OSPF E1 E2 Routes
OSPF is a major topic on both the CCNA and CCNP exams, and it's also the topic that requires the most attention to detail. Where dynamic routing protocols such as RIP and IGRP have only one router type, a look at a Cisco routing table shows several different OSPF route types.

Wireless Home Networking Choosing The Right One
Are you suffering from a home wireless networking nightmare? There are so many options. 802.11a, 802.11b, 802.11g - what is all that? All you want is to get online on your notebook computer in your living room without tripping over wires.

Cisco CCNA / CCNP Home Lab: Why You Need An ISDN Simulator
ISDN is a vital topic for today's CCNA and CCNP candidates, especially for the ICND and Intro exams - you've got to know ISDN inside and out to pass those exams. Naturally you want to include it in your home lab.

12.07.05

Router On A Stick

By Chris Bryant

For CCNA and CCNP candidates, it's hard not to laugh the first time you hear the phrase "router on a stick".

Let's face it, that's a pretty silly term. But as those who have passed the CCNA and CCNP exams know, this is a vital exam topic that you must know how to configure and troubleshoot.

Basic Cisco theory states that for hosts in different VLANs to communicate, a Layer 3 device must be involved to handle the routing between the VLANs. That device is a router, and there are special considerations that must be taken into account for both the physical router itself and the configuration you'll be writing.

The router will be connected to a switch via a FastEthernet port (or higher). The router port cannot be a regular Ethernet port, since the router port will need the ability to send and receive data at the same time.

The configuration of the interface is where things get interesting. Let's say we have two VLANs that will be using router-on-a-stick to communicate. Here is the VLAN information:

VLAN 20: 20.20.20.0 /24

VLAN 40: 40.40.40.0 /24

The port on the switch that will be connected to the router's FastEthernet port must be in trunking mode, and you must know the trunking protocol in use. We'll go with the Cisco-proprietary ISL here.

Available from BrightTools, Activeworx Security Center includes new features for meeting SOX and HIPAA compliance requirements, improved tools for forensic investigation, and much more.

The physical FE port on the router will not have an IP address. The use of router-on-a-stick mandates the use of logical subinterfaces. While we don't have to use the VLAN numbers for the subinterface numbers, I've found this helps you keep the interfaces straight. One subinterface must be given an IP address in VLAN 20, and the other will have an IP address in VLAN 40.

After creating subinterfaces fast 0.20 and fast 0.40, the config looks like this:

interface fastethernet0

   no ip address

interface FastEthernet 0.20

   ip address 20.20.20.1 255.255.255.0

interface FastEthernet 0.40

   ip address 40.40.40.1 255.255.255.0

Believe it or not, you're almost done! Now we need the encapsulation statement under each subinterface. The subinterface statement must reflect both the VLAN number and the encapsulation type being used. When we're finished, the config would look like this:

interface fastethernet0

   no ip address

interface FastEthernet 0.20

   ip address 20.20.20.1 255.255.255.0

   encapsulation isl 20


interface FastEthernet 0.40

   ip address 40.40.40.1 255.255.255.0

   encapsulation isl 40

And that's it! Your hosts in VLAN 20 should now be able to communicate with hosts in VLAN 40, and vice versa.

A couple of final troubleshooting points - the most common error with router-on-a-stick is to put the wrong vlan number in the encapsulation statement. Also, make sure you have configured the router's IP address in VLAN 20 as the default gateway for hosts in VLAN 20, and do the same for VLAN 40.

I hope you've enjoyed this look at router-on-a-stick. While the name may get a chuckle out of you, it's still used in quite a few networks out there, and knowing how to configure and troubleshoot it will get you that much closer to earning your CCNA and CCNP.


About the Author:
Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (www.thebryantadvantage.com), home of FREE CCNA and CCNP tutorials and The Ultimate CCNA Study Package. (CCNP Study Packages are on the way!) Video courses and training, binary and subnetting help, FREE tutorials, and corporate training are also available.

About NetworkNewz
NetworkNewz editors, writers and contributors focus on both the big picture and the details of networking. At NetworkNewz our goal is to deliver to you The Key To Network Management.

NetworkNewz is brought to you by:

SecurityConfig.com NetworkingFiles.com
ITmanagementNews.com WebProASP.com
DatabaseProNews.com SQLProNews.com
ITcertificationNews.com SysAdminNews.com
LinuxProNews.com WirelessProNews.com
CProgrammingTrends.com ITmanagementNews.com


-- NetworkNewzis an iEntry, Inc. publication --
iEntry, Inc. 2549 Richmond Rd. Lexington KY, 40509
2005 iEntry, Inc.  All Rights Reserved  Privacy Policy  Legal

archives | advertising info | news headlines | free newsletters | comments/feedback | submit article
The Keys To Network Management Ask Questions in the Networking Forum NetworkNewz News Archives About Us Feedback NetworkNewz Home Page About Article Archive News Downloads WebProWorld Forums Jayde iEntry Advertise Contact