From what I've seen interacting with other engineers, it seems that most of us, when we need to research something relevant to Cisco networking, go straight to Google. This is typically the most expedient path toward an answer, but it isn't necessarily the most reliable or the most accurate. The problem is that Google or another search engine will direct you to whatever resource on cisco.com it considers most relevant; one must be careful to consider the hardware platform and/or IOS version specific to the situation at hand.
For example, an engineer who googles for documentation concerning the configuration of a particular IOS feature will often find what he needs, but may not be aware that the documentation he is looking at is for a newer or older version of software, or that it applies to a family of hardware different from the device he is configuring. This might not be a problem all the time, but it is a good way to get bitten by minor differences in supported features and configuration syntax.
A more reliable approach is to navigate Cisco's documentation manually to find the exact information you need. People often complain that Cisco's online documentation is too difficult to navigate, but after digging through it numerous times to find references for the many blog articles I've written, I think it merely takes a bit of strategy. That's why I decided to write this article.
Starting at http://cisco.com/, select Support from the navigation menu at the top of the page. This brings you to Cisco's main support page, which is essentially a collection of pointers to other places all around the site. The portion of the page we're most interested in is the part with two blue boxes of links:
Two navigation options are presented to the user here. The first option is to navigate by product or technology name (e.g. routers, security, wireless, etc.). This option also includes the ability to search. The second option is to navigate by task (e.g. troubleshoot, configure, design, etc.).
This is, in my opinion, bad design; if a user intends to configure a router, which link is he supposed to follow, "Routers" or "Configure"? That question is ultimately moot, because all of these links (with the exception of "Download Software") effectively all point to the same place anyway. Like I said, this page is just a collection of references to other resources on cisco.com; the master documentation index is actually at http://www.cisco.com/cisco/web/psa/default.html.
Depending on which link you chose on the prior page, you will be directed to a subsection of this master index. Personally, I prefer to always start from the root of the master index itself and dig into whatever I need from there. Note that many of the subnavigation links down the left side of the page are the same links shown on the main support page.
There are two basic paths down which you can begin navigating to the specific documentation you desire: "Products" and "Technology". Choosing "Products" allows one to navigate down a hierarchy of all of Cisco's hardware and software offerings and select the specific device or version of code (e.g. IOS 12.T) for which documentation is desired. The "Technology" path is more general in nature, and is better suited for theory and design discussion for technologies which span many products.
As it is obviously impractical to provide a complete list of what can be found where in the world of Cisco documentation, hopefully a few common examples will suffice.
Example 1: Configuring EIGRP on a Router
You might assume that to find the documentation for this, you should navigate to "Products" > "Routers" and select your specific platform (for example, the 2800 series). However, this is not the case. Most aspects of IOS configuration will be the same across all routers running the same version of IOS, regardless of the underlying hardware platform. For this reason, most IOS (and other operating system) configuration tasks are found under "Products" > "Cisco IOS and NX-OS Software".
Selecting the major version of software you'll be working with (as indicated by the output of
show version on the device to be configured) takes you to the introduction page for that software. This example assumes IOS 12.4T is in use.
From here, select "Configuration Guides" to see the collection of configuration guides available for this version of IOS. Select the guide most relevant to the task to be performed. For the purpose of this example, we want "Cisco IOS IP Routing: EIGRP Configuration Guide, Release 12.4T".
This takes us to the manual specific to EIGRP configuration on IOS 12.4T.
The manual can be viewed online, navigated using the links at left, or optionally downloaded in part or entirely as a PDF file. A word of caution: while it may be tempting to download all available manuals in PDF for offline access, make sure that they are refreshed from time to time as the online documentation is updated and corrected.
To summarize, the path we followed to find the correct documentation for our example is:
- Cisco IOS and NX-OS Software
- Cisco IOS
- Cisco IOS Software Release 12.4 Family
- Cisco IOS
- Cisco IOS and NX-OS Software
Example 2: Configuring a Catalyst 3560
Catalyst switches are approached differently from routers, as much of their available features and configuration options may vary from platform to platform. If we look again under "Products" and navigate to the IOS version in use on the Catalyst switch, we see that the section is lacking any configuration guides.
To access the configuration guides for switches, we must first navigate to "Products" > "Switches", and select the model of switch we wish to configure. On the introduction page for that model, we then follow "Configuration Guides" and select the specific version of IOS running on the switch. This example assumes IOS version 12.2(52)SE.
This directs us to the manual specific to both our hardware platform and the version of IOS which it runs.
Example 3: Researching the Purpose of a Command
Assume we notice the command
no ip unreachables present in the configuration of an interface on a router, and wish to learn more about its purpose. Starting once more at the root of the master documentation index, we navigate to "Products" > "Cisco IOS and NX-OS Software" and select the relevant major version of IOS. Whereas the first example had us looking for a configuration guide, this time we want a command reference.
There are two ways of locating a command. If you know the general category of the command, select "Command References" and find the relevant reference. If not, select "Master Index" and select "Cisco IOS Master Command List" for the appropriate software release. Commands are sorted alphabetically within the reference (omitting the leading negation keyword
Note that the master command reference is not a redundant resource; following it ultimately directs you to the correct categorized reference for a command.
Hopefully these examples have provided a better understanding of how Cisco's documentation is arranged, and how to navigate it more easily.