Networking Knowledge Base

ResolutionFor answers to frequently asked questions, refer to OSPF: Frequently Asked Questions.

Core issueThe ability to apply sequence numbers to IP access list entries simplifies access list changes. Prior to the IP Access List Entry Sequence Numbering feature, there was not a way to specify the position of an entry within an access list.A Ci...

Core IssueThe router fails to load a previously saved configuration. One of these error messages may be observed:System Bootstrap, Version 11.1(8)CA1, EARLY DEPLOYMENT RELEASE SOFTWARE (fc1) Copyright (c) 1997 by cisco Systems, Inc. Warning: monitor ...

Core issueIn the switch, there areonly two monitor (SPAN) sessions available. If the switch has a VPN module inserted into a chassis with Switch Fabric Module, then the VPN module uses one of the monitor (SPAN) sessions. This Switched Port Analyzer (...

Core issueDevices are discovered by polling Cisco Discovery Protocol (CDP).For the device to be discovered by the application, it needs to have CDP enabled.ResolutionTo resolve this issue, connect to the device and verify that CDP is enabled, as show...

Core issueCisco IOS  quality of service (QoS) offers two kinds of traffic regulation mechanisms traffic policing and traffic shaping. A traffic policer typically drops traffic that violates a specific rate. A traffic shaper typically delays excess tr...

Core issueIn rare circumstances, Cisco Catalyst 6000 Series switches can experience a red status light on the supervisor module due to an NVRAM checksum error.These are the results of this condition:The output of the show version command shows a chec...

ResolutionYou can check if the port is set to ErrDisable by using the CISCO-STACK-MIB. Refer to the object information, as shown: portAdditionalOperStatus OBJECT-TYPE   SYNTAX OCTET STRING(SIZE(1..2))   -- BITS are:   -- other(0)   -- connected(1)   ...

Core issueCertificate Authorities (CAs) manage certificate requests and issue certificates to participant network devices. Specific CA servers are referred to as trustpoints.When a connection attempt is made, the secure HTTP (HTTPS) server issues a c...

Core issueCatalyst 6500 Series Switches with Supervisor Engine 720 and service modules can experience connectivity issues between the service modules and the rest of the network in certain scenarios:Scenario 1 When the Distributed Forwarding Card 3 (...

ResolutionThe SPAN reflector feature enables multicast traffic as well as other traffic that requires central rewrite engine to be switched when it comes from the Firewall Service Module (FWSM).  For example, for each FWSM in a switch, the SPAN refle...

Core IssueNetwork Address Translation (NAT) replaces IP addresses within a packet with different IP addresses. It is useful for conserving IP address and connecting a private network using an unregistered address to a public network like the Internet...

Core IssueThe console port setting and terminal settings do not match.ResolutionTo resolve this issue, perform these steps:Open the Hyperterminal on the PC, or other terminal emulator, and use these settings:       Speed: 9600 bps               Datab...

ResolutionIn order to enable VLAN communication between switches in different Virtual Trunking Protocol (VTP) domains, add the VLAN manually on each switch.In spite of a VTP domain mismatch, VLAN communication works well. Only VTP updates are not pro...

Core issueThese errors indicate a hardware problem or one of these problems:Duplex mismatch   Faulty cable    Type 1 cabling   Faulty ports   Hardware problem of an external connected deviceClock failure on the SupervisorThese errors are most commonl...