Networking Knowledge Base

Core issueThe unknown status is displayed by the show trunk [mod/port] detail command in these fields:peer-port mode encapsulation status Sample output:Switch (enable) show trunk 2/1 detail* - indicates vtp domain mismatchPort  Mode  Encapsulation  S...

Core issueThe router crashes when Simple Network Management Protocol (SNMP) requests of IP Service Level Agreements (SLAs) MIB CISCO-RTTMON-MIB.my are sent to the router. This happens when an SNMP set is used to create an IP SLAs probe. The router do...

ResolutionVariable-Length Subnet Masks (VLSMs) allow the use of different masks for the same network number on different interfaces, which allows the user to conserve IP addresses and more efficiently use available address space. Enhanced Interior Ga...

ResolutionThe Multicast Expansion Table (MET) is used for multicast packet replication. The table gets populated when a valid multicast entry needs to be programmed into the hardware forwarding table of the switch. If the %MLS-2-MCAST_METFULL message...

ResolutionWhen active links are aggregated into an EtherChannel, the ports momentarily leave the Spanning Tree and join back as a single, logical port. Until the Spanning Tree reconverges, the network traffic is disrupted. On the other hand, if a LAN...

Core issueRelay agents are used to forward requests and replies between clients and servers when they are not on the same physical subnet. Relay agent forwarding is distinct from the normal forwarding of an IP router, where IP datagrams are switched ...

Core IssueThe process can register to be notified when various events occur. SCHED-3-THRASHING error messages mean that the indicated process relinquished control 50 consecutive times, and there were still outstanding events to be processed.Resolutio...

Core issueThe redundant Route Processors (RPs) have different memory configurations. To support the high availability feature, it is recommended that both RPs have the same memory configurations. This issue is specific to MSFC2. It is not neccessary ...

Core issueIn the 2007 calendar year, daylight saving time (DST) rules can cause Cisco IOS® and the Catalyst operating system (CatOS) to generate timestamps, such as those in system log messages, that are off by one hour.In Cisco IOS, the clock summer...

Core IssueThese are the most likely causes:Misconfigured IP address Physical layer problemsResolutionTo resolve this issue, perform these steps:Ensure that the IP address is configured correctly on the destination device.Check the physical connectivi...

Core issueThe issue may occur for these reasons:This message indicates that the VLAN is configured with Private VLAN (PVLAN), and that the Router Access Control List (RACL) for this VLAN cannot be configured in the Policy Feature Card (PFC). The RACL...

ResolutionThe DTP-1-ILGLCFG: Illegal config (on, isl--on,dot1q) on Port [mod/port] message can occur if both sides of the trunk are set to on, but the encapsulation types (isl, dot1q) do not match.To resolve this issue, check the output of the show t...

Core issueSTP does not allow loops to be formed when switches or bridges are interconnected through multiple paths. STP implements the 802.1D IEEE algorithm, as Bridge Protocol Data Unit (BPDU) messages are exchanged with other switches to detect loo...

Core issueSpanning tree delays may cause a workstation to report a No DHCP Servers Available message.ResolutionA workstation may report a No DHCP Servers Available message when booting up because of Spanning Tree Protocol (STP) loop detection delays....

Core IssueWhen running Open Shortest Path First Protocol (OSPF) between routers connected over a Frame Relay network, if the network is defined as a broadcast network, it is necessary to use the [broadcast] keyword in the frame-relay map commands.Res...