Section 25 OBJ 5.7: Troubleshooting Networks Flashcards
Wired Connectivity Issues
Physical Connection: Think about every piece in that physical connection.
NIC -> RJ45 Port -> ethernet cable -> patch panel -> switch -> router
Test with network cable tester
Look at back of network interface card (NIC). It will have 2/3 lights, a link light, activity light, and sometimes a speed light
Cable Length: cable length may exceed maximum.
Use repeater to extend range if exceeding maximum
Interference: Power lines, fluorescent lighting, motors, generators
Verify cables are not going across any power lines or fluorescent lights.
If they must be in those locations, use fiber optic to avoid interference
Port Flapping: intermittent connectivity issue between client and switch. Means the status is flipping from on to off
Usually caused by bad cabling, external interference, or a faulty NIC
Network Performance Issues
Manifesting as a slowdown on the network
Different issues:
1. Mismatched duplex setting: either on NIC or switch port interface
Can be set to half/full duplex. Half means cant send/receive at same time
2. Mismatch speed setting: when a client connects to the network, they negotiate on what speed to operate at.
3. Network adapter drivers are out of date: drivers may be old and need updating
4. Malware infection: run antivirus software
Break problem into three main groups:
Single Client: look for individual duplex settings, speed settings, network adapter drivers, and malware
Network Segment: Look for the single switch settings
Entire Network: Look for the router, gateway, or firewall
Wirelessly Connectivity Issues
- Intermittent wireless connectivity: connected or disconnected network
- Signal interference: something is causing issues with our signal
Ensure the wireless network is operating on the correct channels
Interference can also be physical - Low Signal Strength: Measured with Received Signal Strength Indicator (RSSI), which is used to measure the signal strength based on an index level and is shown in dB.
High value = better signal, low noise
Low value = worse signal, high noise
In order to increase signal strength, increase power of transmission, increase antenna size, or move closer to the source. - Standards mismatch: Check which versions of wireless networking are being used.
Can configure the wireless access point to only support modern versions of the protocols.
Backwards compatibility will affect other devices
If a device on 2.4 GHz forces the router to downgrade, all devices on 2.4 GHz connected will downgrade
Voice Over IP (VoIP) Issues
Two major quality issues:
1. Latency - time for signal to reach client
Keep latency under 50-100 ms
2. Jitter - Measurement of the variation of delay over time
To solve:
1. Increase network performance
2. Implement quality of service - can set network configs for what traffic will be prioritized
