Ch. 3.4 Flashcards
What does UPS mean?
What are UPSs good for?
Uninterruptible Power supply
Providing enough power to switch secondary power source or shut down system gracefully avoiding data loss
How do you troubleshoot network adapter? (2)
Verify &/ Reinstall network drivers
Check status LED
How do you troubleshoot the Data Link Layer?
Check the topology of your network and identify which part is affected
Port Status: What do these statuses mean?
Solid Green
Flickering Green?
Solid Green - Connected with no traffic
Flickering Green - Link is operating normally with traffic
Port Status: What do these statuses mean?
No Light
No Light - Link is not working or port is shut down
Port Status: What do these statuses mean?
Blinking Amber
Solid Amber
Blinking Amber - Fault has been detected
Solid Amber - Port is blocked by spanning tree algorithm.
Switch commands: What do these commands do?
show config
show startup-config
VS
show running-config
show config: displays switch configuration
show startup-config VS show running-config
The startup config could be different than what’s running now
Switch commands: What do these commands do?
show interface
show interface: lists state of all interfaces and report configuration details
Switch States: What does it mean?
Down/down
What are 2 possibilities of this issue?
There is no link.
Usually due to no host being attached.
Could be caused by speed mismatch
Switch States: What does it mean?
Administratively down/down
How do you bring it back up?
Interface has been disabled using shutdown command.
Use “no shutdown” to bring it up
Switch States: What does it mean?
Down/Error Disabled
What are 2 possibilities of this issue?
Interface is disabled due to error.
Usually due to STP or Port Security violation issue
Switch States: What does it mean?
Up/down (Suspended)
What is one command used to investigate?
Port is part of a link aggregation group and channel hasn’t been negotiated.
Command “show etherchannel” to investigate the cause
What are Interface Error Counters good for?
Recording data to troubleshoot
Why might collisions happen? (3)
If duplex setting on switch port and host are mismatched
If legacy hub or host NIC is connected to a switch
Configuration error at lvl 1 or 2 OSI model
Interface Counters: What does Link State mean?
What are 2 ways you can troubleshoot through Link State?
Measures whether an interface is working or not.
Can configure an alert if an interface goes down.
Track uptime/downtime %
Interface Counters: What do Resets track?
When should they be investigated?
When might they restart automatically?
Amount of times an interface have restarted over the counter period.
Anything but occasional resets
If traffic is very high or large number of errors
Interface Counters: What do Discards/Drops mean?
4 Reasons
Could be
1. Checksum Errors
2. Mismatched MTUs
3. High Load
4. Permissions
When is a CRC calculated?
Calculated by an interface when it sends a frame
What are CRC errors usually caused by? (2)
Usually by interference.
- Poor quality cable: Termination & Attenuation
- Mismatches of physical hardware
What is a Runt?
A frame that is smaller than minimum size (64 bytes for internet)
How is a runt frame usually caused? (2)
By collision
Possible driver issue
What is a giant?
A frame that is larger than the maximum allowed size for the receiving interface
What are 2 causes of a Giant frame error?
Jumbo Frame configuration errors
Ethernet Trunks
What is the first possible error by a Giant frame in detail?
How can you resolve it?
Jumbo Frame - When a host is configured to use jumbo frames but the switch isn’t.
Use command “show interface” to see if jumbo frames are accepted on the particular port
What is the second possible error by a Giant frame in detail?
How can you resolve it?
Ethernet Trunks - Trunk links carry traffic from switches and routers.
They use 802.1Q framing for VLAN and adds 4 bytes to header making maximum 1,522 bytes
If one side doesn’t use 802.1Q, frame will look too large for the other. Configure both
What does CAM stand for?
What does it represent?
Content Addressable Memory
The table of the MAC addresses for switches
What is a Network Loop?
When flooded frames circulate the network infinitely
What is a broadcast storm?
Flooded frames looping
If a frame loops, what should happen?
STP should shut down the port.
Isolates problem to segment of the network
What should you do in case of a broadcast storm with STP? (3)
Verify STP is enabled
……………………………….
Verify physical configurations of legacy equipment
……………………………….
Verify user equipment is not part of the loop
Ie. Unmanaged desktop switches / VoIP handsets
Will thin or thicker thermal conductors improve thermal performance?
Thicker as they can withstand more heat.
What cabling is recommended for PoE+?
Cat 5e or better.
Cat 6A is recommended
What is the typical power budget for each switch?
300-400 watts
What happens when power budget is exceeded on a switch?
Some devices may not activate
Intermittent Resets
What command reports power budget and consumption?
show power inline
