Networking Knowledge Base

Core issueA Private VLAN (PVLAN) is a VLAN with configuration for Layer 2 (L2) isolation from other ports within the same broadcast domain or subnet.Assign a specific set of ports within a PVLAN to control access among the ports at L2. PVLANs and nor...

Core issueSpanning-Tree Protocol (STP) loop or misconfiguration causes a Catalyst 5000 to log %MLS-4-MOVEOVERFLOW:Too many moves messages.ResolutionMessages similar to the following are output on a Catalyst 5000 switch:05/13/1998,08:55:10:MLS-4:Too m...

Core issueAutomatic medium-dependent interface crossover (Auto-MDIX) is a feature that allows the switch interface to detect the required cable connection type (straight-through or crossover) and automatically configure the connection appropriately. ...

AnswerThe new 48-port 10/100/1000BASE-T line card (WS-X4548-GB-RJ45) differs from the old 48-port 10/100/1000BASE-T line card (WS-X4448-GB-RJ45) in these ways:It is Time Domain Reflectometer (TDR)-capable, with TDR support available in a future softw...

SolutionCatalyst OS (CatOS) does not support setting individual passwords for console and Telnet. The set password command sets a common password for console and Telnet access. This is an example of how to set the login password on the switch:Console...

Core issueThe encapsulation option does not show up when trunking is configured on a trunk port in the WS-X6148-GE-TX module. This is because the encapsulation option is enabled by default. Two trunking encapsulations are available on all Ethernet p...

Core issueOn the Cisco Catalyst 4500 Switch with Supervisor V-10GE, when a 10-Gigabit Ethernet port is configured other than the interface Tengigabit1/1, these error messages are received in config mode:Switch(config-if)#interface TenGigabitEthernet1...

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...