Networking Knowledge Base

Core issueThe message probably displays because the Multilayer Switch Feature Card (MSFC) is in boot mode. The message can also occur if there is a missing bootflash image.ResolutionIf the MSFC boots in boot mode, change the boot variable settings to...

Core issueThe issue is due to the corrupted non-volatile RAM (NVRAM) and this error message may be generated in either of these scenarios:While trying to convert the Supervisor 720 from a native Cisco IOS  software release to hybrid, it fails to acce...

Core issueA misconfiguration or a physical layer issue may cause the alignment error counter to increment.ResolutionAlignment errors are the count of the number of frames received that do not end with an even number of octets and have a bad Cyclic Re...

Core issueA misconfiguration on a switch can cause the configuration updates of the VLAN Trunk Protocol (VTP) to fail. A common problem in most cases is that the new VLAN created in the VTP server switch does not propogate to the VTP client switches,...

Core issueOn a Catalyst 3750 stack, network connectivity can be impacted if the MAC address or VLAN ID associated with an IPv4 or IPv6 addresses were to change,, which causes a change in the ARP and CEF adjacency tables. When the change occurs, the u...

Core IssueWhen configuring the ip helper-address command, the following broadcast packets will be forwarded by the router by default:TFTP - port 69Domain Name System (DNS) - port 53Time service - port 37NetBIOS Name Server - port 137NetBIOS Datagram ...

Core issueThe complete error message canappear like this:%SYS-DFC7-2-MALLOCFAIL: Memory allocation of xxxx bytes failed from 0xYYYYYYYY, alignment x This problem occurs due to the presence of the Cisco bug ID CSCei20107.The problem is that two proce...

Core issueSupervisor 32 (Sup32) boots properly when the software image boots. However, when the Multilayer Switch Feature Card (MSFC) boots, the MSFC goes into the ROM monitor (ROMmon) mode. The MSFC then crashes, and Sup32 enters the ROMmon mode.Thi...

ResolutionA port may go into errdisable status due to a UniDirectional Link Detection (UDLD) condition. The errdisable status indicates that the port was automatically disabled by the switch Operating System (OS) software due to an error condition en...

ResolutionTo configure Spanning Tree Protocol (STP) diameter on Cisco Catalyst switches that run Cisco IOS Software, issue the spanning-tree vlan vlan-id root primary diameter net-diameter command.To configure STP diameter on Cisco Catalyst switches ...

Core IssueLog message timestamps may be configured to display either the date and time or  the router's uptime. If configured for uptime, the log  output is similar to this: 1d23h: %PARSER-3-BADSUBCMD: Unrecognized subcommand 0 in interface command '...

Core issueAll power supply status LEDs should be green. The power supply includes the power supplies and power supply fans. If one or both are red, this can indicate a power supply problem or failure.These are the most common issues:If a power supply...

Core IssueBefore exchanging routing information, routers running Open Shortest Path First (OSPF) form neighbor relationship with other OSPF routers on the same segment by exchanging hello packets. The hello packets contain various parameters. Some of...

Core issueA Catalyst 2940, 2950, 2955, 2970, 3550, 3560, 3750 or 3750 Metro Switch can experience boot errors or can constantly reboot.If the switch does not boot properly, it can be due to one of these reasons:If the switch is unable to load a softw...

ResolutionThese are possible resolutions to this problem:It is possible that the internal devices do not have a default gateway or a more specific route to the destination. Verify that they have a route to the destination in their routing table or th...