Common Network Issues
There are several common network issues you might be called upon to diagnose and resolve.
Network Issue and Possible Problems and Solutions
No network connectivity or connection lost :
This could indicate a physical problem such as a loose cable or a defective network adapter. Check cables and connections and check for link lights on the network adapter. Reset connections, replace cables, or reinstall/replace the adapter as necessary.
On IP networks, check for a missing or incorrect IP address. If the address is manually conﬁgured, this could be a data entry error; reconﬁgure the connection. If automatically conﬁgured, the DHCP server might be unavailable or unreachable. Make sure the DHCP server is up and that the client is physically connected to the network.
Network communications are slow :
The network might be experiencing high traffic and many collisions. Check the activity status indicator light for the collision frequency. This should be a temporary condition that will pass; if not, network engineers might need to upgrade the network bandwidth or data rate to increase throughput.
Local communications but no Internet connection :
The default gateway address might be conﬁgured incorrectly, the gateway might be down, or there might be a problem with the Internet Service Pro- vider (ISP). Check the default gateway address, verify that the default gateway is functioning, and contact the ISP to ﬁnd out if there are any problem conditions. The proxy settings are incorrect. Check the proxy conﬁguration of your network connection.
Client can connect but cannot access resources :
The user might have insufficient permissions, or the target network resource might be unavailable. Check to make sure the printer or server is running and connected to the network, and check to make sure the user has appropriate permissions.
Connections by IP address but not by name :
The DNS conﬁguration is incorrect or the DNS server is down. Or, the hosts ﬁle might be conﬁgured incorrectly. Check the IP conﬁguration settings and verify that the DNS server is running. Check the hosts ﬁle to make sure it does not contain incorrect entries.
Intermittent signal quality issues :
Electrical noise, or electrical interference, is a general term for unwanted signals on the network media that can interfere with network transmissions. Interference or noise can come from natural sources, such as solar radiation or electrical storms, or from man-made sources, such as electronic interference from nearby motors or transformers. Electrical noise can also cause transient power problems. Some of the common sources of noise include:
- Ambient noise can come from many sources, including solar disturbances that affect the earth’s magnetosphere, or nearby radio broadcasting towers.
- Nearby high-tension power lines or a building’s own electrical wiring can create electrical noise.
- Electric motors, such as those used in elevators, refrigerators, water fountains, and Heating, Ventilating, and Air Conditioning (HVAC) equipment, create noise while running, but it is worse when they start up. Motors require a huge amount of electricity to start up, causing a burst of noise. These bursts can create short temporary outages that resolve themselves when the motor reaches full speed or stops.
- Like electric motors, electric heating elements use a lot of electricity and thus cause a signiﬁcant amount of noise while running.
- Fluorescent, neon, and high-intensity discharge (HID) lights produce a large amount of electrical noise, generally due to the transformers and ballasts required to make these lights work.
To prevent or reduce noise, use Category 5e or better twisted-pair cable, which has more twists per inch than Category 3. Also, use shielded twisted pair where sources of interference are high. Do not run data and power cables in the same conduits, and run network cables parallel to each other whenever possible. Keep network cables at least 20 inches away from ﬂuorescent lights. Ground all equipment and electrical circuits according to the manufacturer’s instructions and local building codes. Do not unwind cable any more than necessary to make connections to other devices.