Networking Knowledge Base

Core issueThese are the requirements for the VLAN interface to be up/up:The VLAN must exist in the VLAN database and must be active.At least one port must be assigned to the VLAN.The VLAN must contain an active device.ResolutionFor information on how...

Core issueThe error message may look similar to this:%SYS-3-PKTBUFFERFAIL_ERRDIS:Packet buffer failure detected. Err-disabling port [Module/Port].%SYS-4-PKTBUFFERFAIL_WARN:Err-disabled ports with packet-buffer failure. Module [Num] can be power cycle...

Core issueGiants are the frames that are greater than 1514 byte on a non-jumbo port.Prior to the the 12.0(5.2)XU release, the switch would discard frames larger than 1514 bytes.These counters are incremented in 10/100 ports when the port is configure...

Core IssueThis is most likely caused by a Network Address Translation (NAT) misconfiguration, such as permitting any packets in the Access Control List (ACL) used for NAT.ResolutionPermit only the necessary subnets to translate.For information on NAT...

Resolution:To enable a label switch router (LSR) to send Simple Network Management Protocol (SNMP) notifications or informs to an SNMP host, use the "snmp-server enable traps" command in global configuration mode.Optionally you can also specifies the...

Core issueImproper Catalyst OS (CatOS) configuration results in the inability to establish a trunk link connection.ResolutionTo resolve this issue, perform these steps: If the user is unable to establish a connection across a trunk link, check the se...

Core IssueA system crash is when the system detects an unrecoverable error and restarts itself. A crash can be caused by software problems, hardware problems, or both. This section deals with hardware-caused crashes and software-related crashes, but ...

Core issueDuring the attempt to configure multiple switched virtual interfaces (SVIs), this produces a command-line interface (CLI) error message as shown in this example:Forcing SVI 7 to stay shutdown (SVI 551 tied to line card in slot 1.)For securi...

Core IssueAny interesting IP traffic, if not explicitly denied on a dialer list, brings up the dialer interface. Enhanced Interior Gateway Routing Protocol (EIGRP) hellos and updates act as interesting traffic and initiate an ISDN connection on a BRI...

Core IssueThe Cisco IOS  Software image is not appropriate for the router, or it is corrupted.ResolutionErase the Flash, and download a new valid Cisco IOS Software image.  For information on how to erase the Flash, refer to PCMCIA Filesystem Compati...

Core IssueWhen a router forwards a multicast packet from one interface to another, it decrements the Time To Live (TTL) value in the IP header by one. It sends the packet only if the resulting TTL value is not zero and is greater than the multicast T...

Core IssueIf a Cisco IOS  Software upgrade is performed by issuing the xmodem command from ROM Monitor (ROMmon) mode, and the router boots successfully but no image is in the Flash, then the [-r] option was used when the xmodem command was issued.The...

Core IssueThe issue occurs when an Asynchronous Transfer Mode (ATM) exists in the 7200VXR and attempts are made to set an external clock or clock from the line, but the clock status appears to still be internally clocked.In order to confirm the Cisco...

ResolutionThis example shows how to configure the FastEthernet port on an 1841 router as a trunking interface. The Cisco 1841 router has two onboard FastEthernet autosensing interfaces that support 10- or 100-Mbps connections.The sub interface become...

Core issueThe crash occurs when a vlan.dat NVRAM file is corrupt. One important step is missing in the Step-by-Step Procedure to Convert from CatOS to Cisco IOS System Software in System Software Conversion from CatOS to Cisco IOS for Catalyst 6500/6...