ccna wireless 640-722 official cert guide

ccna wireless 640-722 official cert guide.At this point, you know how to set up a VLAN-based network, but you will inevitably encounter failures related to VLAN configuration.To determine the cause of the failure, you should do the following checks in turn. 1. Check the status of the interfaces to determine if the problem is at the physical layer. 2. Check the switch and router configurations to confirm that no additions or modifications have been made. 3. Verify that the trunk connection is operating properly.4. Verify that the VLANs are configured correctly and that the Spanning Tree Protocol (STP, discussed in Chapter 13) is operating properly. The next few subsections describe some basic checks that should be done whenever a switching failure is encountered.1. Performance ProblemsWhen experiencing slow or intermittent connectivity problems, you should first use the command showinterfaces to check the statistics of the switch interfaces. Is the number of errors (such as conflicts) large?There are various reasons for these problems. the most common is a duplex mode or speed mismatch at both ends of the connection. Please check the settings on both ends of the connection and also make sure that the correct type of cable is used: crossover cable when connecting a DTE to a DCE; crossover cable when connecting a DTE to a DTE or a DCE to a DCE (this is described in Chapter 4) Make sure that the cable does not exceed the length limit and also make sure that there is no hardware failure on the connected NIC.2. local connection problemsIf all you see on the terminal when trying to access the console port of the switch or router is garbled, it may indicate that the terminal is not set up correctly-the culprit is usually an incorrect baud rate setting. Some devices allow operating system upgrades to be performed through the console port, and other administrators do this because they may have changed the baud rate to the maximum possible value and forgotten to change it back to 9600 bit/s when they were done. if you are not sure what value to set the baud rate to, keep tweaking it until you find the correct speed.If you are having problems accessing devices in a switched network, you should consider several things. First, is the device to be accessed located in the same VLAN as the current device? If so, make sure that the IP addressing scheme used in this VLAN is correct and that the two devices that are going to share information have placed their ports in the same VLAN. If both devices are Cisco devices, you can use the command show cdp to learn this information, such as IP addresses, through CDP (this is discussed in Chapter 16). Is the switch informed of the devices in the network? You may need to check the CAM table to confirm that connectivity issues are not the result of a security violation (see Chapter 11).To check VLAN information, use the show command on the switch to view the VLAN configuration. Alternatively, check the VLAN configuration on each switch using the command show vlan to confirm that the VLAN configuration parameters are the same on different switches. If the port LED is amber, the problem may be that the VLAN to which the port belongs was deleted and the port was not reassigned to another VLAN o Other problems can cause the port LED to turn amber, such as STP switching the port to a blocked state (see Chapter 13) or the port being disabled for a security violation (see Chapter 11). In fact, if many port LEDs are amber, the problem is likely to be a VLAN that has been removed. To determine if the problem is a deleted VLAN, use the command showinterfaceswitchport: If the VLAN to which the port belongs is inactive, as in the following, you have found the culprit.