Networking Knowledge Base

Core IssueThis issue occurs when the boot ROM version on the 2600 series router is not properly comparing the checksum.ResolutionIf the tftpdnld command fails with the TFTP copy: operation terminated due to bad checksum comparison error message, perf...

ResolutionThe new Cisco Catalyst Express 500 Series switches provide smart, simple, and secure networking for customers with up to 250 employees. This new series of Layer 2-managed Fast Ethernet and Gigabit Ethernet switches offers nonblocking, wire-...

Core IssueThis issue is most likely caused by fragmentation of packets needed to pass traffic, but the Don't Fragment (DF) bit is set.ResolutionIncrease the Maximum Transmission Unit (MTU) to 1524 or use Policy-Based Routing (PBR) to clear and set th...

Core issueA VLAN data file residing in Flash prevents the Catalyst fixed configuration switch series from returning to factory defaults after a write erase and reload.ResolutionCatalyst Fixed Configuration Switches 2900XL, 2940, 2950, 2955, 2970, 350...

Core issueThe error message occurs when the user attempts to copy the configuration which was stored in the bootflash to the TFTP server. This is due to the file in the bootflash or Flash has got crashed due to some reasons. So the switch is not able...

Core IssueThe minimum boot ROM version is 12.1(3r)T1, and the minimum Cisco IOS  Software version is 12.1(3)T. If the boot ROM supports the 32 MB Flash SIMM, but the Cisco IOS version does not, the router boots with a valid image on Flash. However, n...

Core issueA master loop breaker election causes the %GIGASTACK-6-LOOP_DETECTED: Gigastack GBIC in interface name is selected as Master Loop Breaker message to be displayed on the elected switch.ResolutionIn a redundant loop configuration, an electio...

Core issueSynchronous Optical Network (SONET) is a high-speed TDM physical-layer transport technology, inherently optimized for voice. Packet-over-Sonet (PoS) provides a means to use the speed and excellent management capabilities of SONET in order t...

Core IssueBorder Gateway Protocol (BGP) is an inter-autonomous system routing protocol used to exchange network reachability information between routers.  BGP uses Transmission Control Protocol (TCP) as the transport protocol (TCP port 179). BGP rout...

Core issueThe breakpoint means an attempt to execute BREAK instruction.This problem is caused when an internal 32 bit counter overflows and wraps around to 0. This counter is not related to user traffic. Typically, this counter reaches the maximum an...

Core issueThe error message occurs when the Fabric controller reports that a fabric channel lost synchronization. This error usually points to a mis-seated linecard. In most cases, you can physically reseat the linecard in order to solve this problem...

ResolutionThe DUAL-3-SIA error message indicates that an Enhanced Interior Gateway Routing Protocol (EIGRP) route is in the Stuck In Active (SIA) state. This means that an EIGRP router has not received a reply to a query from one or more neighbors wi...

Core IssueThe Border Gateway Protocol (BGP) scanner process goes through the BGP table to verify next-hop reachability. This can cause high CPU conditions. When the BGP scanner runs, low priority processes, such as Internet Control Message Protocol (...

Core issueThe complete error message looks like this: %MLSM-6-MMLS_MODE_CHANGE: MMLS: Replication Mode Change Detected because oir eventThis means that the multicast replication mode of the switch has changed.  There are two ways to replicate traffic...

Core issueIf the configuration shows a port to be enabled, but the software on the switch detects an error on the port, the software shuts down that port. In other words, the port is automatically disabled by the switch operating system software beca...