Troubleshooting Performace Issues

Question 1

What do collission and Late collision indicate and how to check them?

Answer 1

Check them with the show interface command.

High collision counters are expected in hub based netorks but not in switch based networks.
Late collisions indicate incorrect cabling, faulty interface or too many hubs.

Question 2

What are Excessive collisions how to show, how to solve?

Answer 2

Excessive collisions occur when a device repeatedly backs off and tretries transmissions up to 16 times. They indicate duplex issues or too many clients on the same collision domain. Disable auto negotiation and set to half duplex

To show excessive collisions use show controller ethernet

Question 3

What are the 3 causes of a broadcast storm how to identify?

Answer 3

• Large Broadcast Domains
• High volume of DHCP requests
• Switching Loops

Drastically increased packet traffic can indicate it, confirm it with wireshark or tcpdump:
tcpdump -i <interface> ether broadcast or ether multicast</interface>

Question 4

What are the main reasons for packet loss?

Answer 4

• Network Congestions
• Faulty Router Configuration
• Bad cables
• Other Hardware failures

Question 5

What are the 5 reasons for Network Performance Issues?

Answer 5

• High CPU usage in networking devices
• High Bandwith utilization
• Poor physical connections
• Malfunctioning of your network
• DNS issues

Question 6

What are typical certificate issues?

Answer 6

• Untrusted authorities
• expired certificates
• missing root certificates