Top 25 Network Problems and Their Business Impact:
| 1. | Configuration not saved
Reboot will cause config to be lost |
| 2. | Saved configurations don’t meet corporate policy
Source of many problems from performance to reliability to security |
| 3. | Bloated firewall rule set; unused ACL entries
Poor firewall performance Open, unused rules, creating potential security problems |
| 4. | Firewall connection count exceeded
New connections via the firewall fail Business applications exhibit intermittent failure at high firewall loads VPNs begin to fail |
| 5. | Link hog - someone downloading music or videos
Slower application response, impacting user productivity |
| 6. | Interface traffic congestion
Unpredictable application performance, impacting user productivity |
| 7. | Link problems & stability
Physical or DataLink errors cause slow or intermittent application performance Link or interface stability can impact routing and spanning tree (see other examples) |
| 8. | Environmental limits exceeded
Fan failure, power supply problems, and high temperatures are indicators of problems that will likely cause a network device to reboot, affecting any applications relying on the device |
| 9. | Memory utilization increasing
A bug in the device’s operating system is consuming more memory and when no free memory exists, the device will reboot, disrupting applications that are transiting the device |
| 10. | Incorrect serial bandwidth setting
Causes routing protocols to make non-optimum routing decisions |
| 11. | No QoS
Important business applications are not prioritized, yielding unpredictable or poor performance during times of interface congestion |
| 12. | QoS Queue Drops
Important business applications are slow Business needs may have changed since the queue definitions were created VoIP is especially affected by this problem |
| 13. | Route flaps
Poor application performance as packets take the wrong or inefficient paths in the network |
| 14. | OSPF recalculations high
Routing protocol unstable; poor and inconsistent application performance |
| 15. | Poor VoIP quality
Due to high jitter, delay, or packet loss Choppy voice calls Calls mysteriously disconnect |
| 16. | Routing Neighbor changes high
Applications using paths via this router will be unstable or slow Affects OSPF, EIGRP, and BGP |
| 17. | OSPF area not connected to backbone
The disconnected OSPF area will not be reachable from other OSPF areas, impacting applications that need to communicate between areas |
| 18. | Unidirectional traffic flow
Typically the result of misconfigured routing Slower applications, strange failure odes, and complex troubleshooting due to asymmetric routing |
| 19. | Router interface down
Any router interface marked administratively up but is operationally down is likely to be a redundant connection that will cause an outage if the other connection also fails, affecting all applications that use it |
| 20. | Unstable root bridge
Bridge priority not set; applications quit working over unstable VLANs |
| 21. | Duplex mismatch
Increasing link errors Applications get slower as traffic volume increases |
| 22. | Downstream hub or switch
Unauthorized devices added to the network Compromise to network integrity and security See 20, Unstable Root Bridge |
| 23. | Port in ErrDisable state
The set of end stations connected via this port are disconnected from the network until the port is enabled (either automatically or by user control) |
| 24. | Unbalanced & unused etherchannels
Increased latency & jitter affecting sensitive applications like VoIP Compromised redundancy |
| 25. | HSRP or VRRP peer not found
Redundancy configured and not operating correctly Outage when a second failure occurs Redundancy compromised |
Free Poster:
The above network problems are available as a snazzy FREE poster (ordered mine) that is suitable for office display and framing, it details the top 25 network problems that Netcordia's NetMRI detects.
It's a great resource for communicating between managers and technical staff, as it illustrates the business impact of common network problems.
Related story:
The major cause of failures are fingers
What do YOU think is a top network problem?
About Brad Reese on Cisco
Brad Reese is research manager at BradReese.Com, advancing the careers of 1 million certified individuals in the growing Cisco Career Certification Program.
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