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