Rounding up the usual suspects - Network Troubleshooting Part 1

When you are troubleshooting a network issue, it can be a little overwhelming if you don't begin the process by narrowing the cause of the problem. You do this by "rounding up the usual suspects", the common causes of network issues.

The Usual Suspects

Taking a queue from the Scientific Method and Occam's Razor , apply the following rule of thumb when localizing and narrowing down the problem: "All things being equal, the simplest explanation is probably the correct one."

Here are a few of the usual suspects:

• Logon Credentials
• The Obvious
• User error (aka PEBKAC)

Logon Credentials

Access to the network depends on a user providing correct logon credentials, normally a username and it's associated password/passtoken. These 2 items must match exactly to what is "on file" with the server that controls network-access, especially passwords, which are case-sensitive. Now technically this usual suspect actually fits into the User error category but user's mistype their passwords so often it is it's own category.

Typical causes of this error are :

1. CAPS Lock is On.
2. User simply mis-typed 1 or both items.
3. User forgot the correct password after having to recently change it due to company password policy enforcement.

The Obvious

Don't neglect the obvious stuff of OSI layer 1 (physical environment) Loose or damaged cables are common causes of physical layer networking issues. Check:

1. Network cables
2. Connectors (cable-end terminators, retaining clips break off of these constantly)
3. Switches installed by users in their workspaces with/without approval
4. Wall jacks (Ethernet)
5. Power plugs

User Error

Among IT professionals you'll hear terms like PEBKAC, ID Ten T , and Layer 8 when describing this usual suspect. One of my favorites is EEOC "Equipment Exceeds Operator Capability" ;)

Simply put, human error accounts for most problems, networking ones included. This issue is partly a problem of user education, as a networking professional it's part of your job to properly educate your end-users on the proper use and expectations of your network. So maybe a better acronym would be PEBAAU "Problem Exists Between Admin And Users" ;)

When you suspect that user error is the cause of a reported network issue, have the user reproduce the issue while you observe him/her. If it turns out to be that the user is following an incorrect procedure or other type of user error, the solution will be fairly obvious. If not, back to the drawing-board.

Good Luck in your networking adventures!