Networking Knowledge Base

Core IssueIntermediate System-to-Intermediate System (IS-IS) recognizes networks as either point-to-point or broadcast. On point-to-point networks, point-to-point IS-IS Hellos (IIHs) are exchanged, while on broadcast networks Level 1 or Level 2 LAN I...

Core issueThe telnet session can hang when you issue the show cam dynamic command in order to display the Dynamic Content-Addressable Memory (CAM) table entries. After you log back in and clear the CAM table with the clear cam dynamic command, you ca...

Core issueWhen the VLAN Trunking Protocol (VTP) mode is changed from VTP client mode to vtp transparent mode, the service providers loose Open Shortest Path First (OSPF) capabilities, but the IP connectivity is unaffected. The OSPF announcements beco...

ResolutionMultilayer Switch Feature Card 1 (MSFC1) does not contain Error-Correcting Code (ECC) memory protection. Therefore, the MSFC crashes if a parity error is detected. These error messages may occur in the following locations:On the console:***...

Core issueThe %GIGASTACK-1-NO_LOOP_DETECT message indicates the link neighbor of link [dec] of  GigaStack GBIC in [chars] did not respond to the loop detection request. If loop  topology is deployed, make sure all switches in the stack are running th...

ResolutionIf you have a Catalyst 6500 switch with different input voltages connected, for example, power supplies (3000W) with 110V/20A inputs, and want to migrate to 220V/20A inputs, then one power supply can be connected to 220 Volts and the other ...

ResolutionTo resolve CNS NetFlow Collection Engine application failures, refer to the Solving CNS NetFlow Collection Engine Problems section of Troubleshooting CNS NetFlow Collection Engine.

Core issueThis is a normal behavior.ResolutionTechnologies such as ATM, frame relay and VLANs introduced a different type of interface, the virtual interface, or sub-interface. On an ATM interface, for example, you can have several permanent virtual ...

Core issueThe %SYS-5-MOD_NOSCPPINGRESPONSE: Module [dec] not responding... resetting module error message indicates that a module does not respond to the Supervisor Engine after three attempts to poll the module. [dec] represents the module number.Th...

Core IssueBuffer tuning allows you to modify the way a router allocates buffers from its available memory, and helps prevent packet drops during a temporary burst of traffic.ResolutionTo see if you might benefit from buffer tuning, use the show  inte...

Core issueOccasionally, unknown unicast or multicast traffic is flooded to a switch port because a MAC address has timed out or has not been learned by the switch. This condition is especially undesirable for a private VLAN isolated port.By default, ...

Core issueThe media type does not appear, or is blank in the output of the show interface status command. However, the interface works fine and there are no connectivity issues.These are some of the reasons for this problem:A non-Cisco Gigabit Interf...

Core IssueThe most common reason an internal Border Gateway Protocol (iBGP) route is not advertised is enabled synchronization. The outbound filter policies can also prevent the BGP from sending updates.ResolutionTo resolve this issue, perform these ...

ResolutionIf the router displays the system bootstrap version and hangs or falls into a booting loop, repeating the same information, the memory may not be well-seated. To address this issue, perform these steps:Re-seat by removing and then re-insert...

ResolutionRedundancy for multicast traffic requires these two things:A unicast routing protocol, for example, Open Shortest Path First (OSPF) or Enhanced Interior Gateway Routing Protocol (EIGRP)Configuration of Protocol Independent Multicast (PIM) o...