Networking Knowledge Base

Core issueCatalyst switches like 3500XL, 2900XL, 2940, 2950, 2970, 3550, 3560 and 3750 do not have a battery-supported system clock. Therefore, they do not maintain the system time on reload. The switch clock has to either be manually set or configur...

Core IssueCisco IOS  Software Inter-Process Communications (IPC) services serve       as the means by which Line Cards (LCs) and the central Route Processor (RP) in       a distributed system communicate with each other. This is done by exchanging IP...

Core IssueIf a dynamic route is lost and no other alternate routes exists for that prefix in the routing table, the router stops forwarding the packets destined for that prefix. It is possible to configure a floating static route that will take over ...

Core issueAn EtherChannel misconfiguration results in a spanning tree loop, which causes the port status to become errdisable.ResolutionThe port status may become errdisable because of an EtherChannel misconfiguration.The errdisable status indicates ...

Core issueThis issue is due to the hardware limitations of Cisco Catalyst switches. Traffic monitoring in a SPAN session has these restrictions:   1.  You can monitor incoming traffic on a series or range of ports and VLANs.  2.  You can monitor outg...

Core IssueThese messages are caused by the improper use of the boot system command.ResolutionTo specify an image for the router to use when booting, use the boot system flash:[filename] syntax.Note: There are no spaces in flash:[filename] to specify ...

Core IssueThe Flash memory problem can be caused by these circumstances:Formatting problemMis-seated Flash cardFaulty hardwareResolutionTo format the Flash disk, issue the format slot[d]: command.Remove and reinsert the Flash disk. Try to format the ...

Core IssueWhenever you install a new card, module or Cisco IOS  Software image, it is important to verify that the router has enough memory and that the hardware and software are compatible with the features you want to use.ResolutionTo check for har...

Core issueA Cisco Catalyst 3560 switch that runs Cisco IOS  Software Release 12.2(20)SE4 or later reloads or resets with the Debug Exception (Could be NULL pointer dereference) Exception (0x2000)! error message.This problem occurs when the Powered De...

SolutionA Catalyst 3750 Switch Stack can be managed either with the web device manager or with the CLI. If you manage the switch with the CLI, you do not need the .tar image. This procedure explains how to copy and upgrade the new IOS  in the Catalys...

Core issueThe Switched Port Analyzer (SPAN) feature, sometimes called port mirroring or port monitoring, selects network traffic for analysis by a network analyzer such as a SwitchProbe device or other Remote Monitoring (RMON) probe.ResolutionIt is n...

ResolutionFor step-by-step instructions on how to configure a Cisco Catalyst switch as a VLAN Management Policy Server (VMPS), refer to the Configure VMPS section of Configuring Dynamic Port VLAN Membership with VMPS.With the VMPS, a Cisco Catalyst s...

Core issueThe message looks similar to this: %SYS-3-SYS_MEMLOW: [chars] usage exceeded 90%This indicates that memory usage has exceeded 90 percent. [chars] can be memory cluster (NMP operating system memory) or mbuf (memory buffer). If memory usage i...

Core issueThe error messages can look similar to this:%SYSTEM_CONTROLLER-SP-3-ERROR: Error condition detected: TM_NPP_PARITY_ERROR%SYSTEM_CONTROLLER-SP-3-EXCESSIVE_RESET: System Controller is getting reset so frequently The most common errors from th...

ResolutionWhen connecting a switch to another switch, a crossover cable must be used. This applies for connecting all like devices, including these:switch to switchworkstation to workstation workstation to router switch to hub hub to hub router to ro...