Networking Knowledge Base

Core issueLayer 3 LAN ports, WAN interfaces and subinterfaces, and some software features use internal VLANs in the extended range. You cannot use an extended range VLAN that has been allocated for internal use.The same VLAN cannot be recreated if it...

ResolutionThere are two methods for converting a non-IOS Access Point (AP) to Cisco IOS  Software:You can use the Wireless LAN Solution Engine (WLSE) web interface and create conversion jobs that you can schedule at a desired time. This method is rec...

Core issueThe connectivity cannot be established when the switch is connected to the Ether Switch Module installed in a router through a straight through cable.ResolutionSince both are switch ports, use a cross over cable in order to establish connec...

ResolutionWhen you telnet to the switch, you have a maximum of three tries or attempts to login with the line password before it displays the message % Bad passwords. The only way to retry is to open another session window.By default only three attem...

Core issueAn improperly seated module or defective hardware may cause these messages to appear in the logs:%SYS-4-NVLOG:SYNDIAGS:Module 1 detected Local Bus Stall%SYS-4-NVLOG:SYNDIAGS:Local Test Mode encounters Minor hardware problem in Module #1 In ...

ResolutionOn the Catalyst fixed configuration switches, you can configure QoS by issuing automatic QoS commands or by issuing standard QoS commands. Catalyst 2940 is the only exception since it does not support automatic QoS commands.With QoS, you ca...

Core IssueCisco IOS  Software does not guarantee 100 percent response to Internet Control Message Protocol (ICMP). Cisco IOS Software is programmed to allocate the main portion of the router's resources to forwarding traffic. This does not affect the...

Core issueWhen DHCP is not correctly configured, a client may not get a valid IP address when booting up. Therefore, client connectivity may not be established. The most common reason for DHCP failure is a misconfiguration on either the DHCP server o...

ResolutionConnectivity issues can often be attributed to routing protocol misconfiguration or misbehavior. However, due to the complexity involved in identifying the cause, this tool does not attempt to resolve such cases. Instead, it focuses on low-...

Core IssueThis problem may be caused by the fact that an Early Deployment (ED) release is required in order to support the hardware. ED releases are indicated by a capital letter following the version number in parentheses. For example, the capital T...

Core IssueThese messages are seen on the console or in the router log. They can be caused by any of these:A dirty filter. A bad fan assembly.A mis-seated fan assembly.A failed Chassis Interface (CI).These are example error messages:%CI-3-BLOWER #[x] ...

Core issueThis error message indicates that the switch forwarding engine receives an IP packet of a shorter length than the minimum allowed length. Therefore, the switch drops the packet. The excessive interrupts are generated by the Enhanced Address...

Core issueEtherChannel configuration errors usually occur because of mismatched parameters on the ports involved. This includes different speeds, different duplexes, and different Spanning Tree Protocol (STP) port values. It is possible that no error...

Core IssueBorder Gateway Protocol (BGP) is an interdomain routing protocol used to exchange network reachability information with configured peers known as BGP neighbors. Unlike other Interior Gateway Protocols (IGPs) used for routing, BGP sends pack...

Core issueThe loadprog: error - on file open error message occurs when the software image is corrupted during an upgrade, or when the software image is not appropriate for the switch. This issue can also be caused by incorrect software handling of un...