This means that all the output is pumped onto the serial cable that is connected to the router. Disadvantage: High load on CPU. Might bring the CPU if the debug output is verbose as the console line has limited data rate and real time output which is more than what the Serial connection can handle slows the performance of the router and causes strain on CPU. This is irrespective of the fact if this is a ssh or a telnet session. Also, compared to console logging this mechanism is not limited to the data rate of Serial line.
Buffer defined should not be too big and should leave enough space so that router has enough free memory for other memory intensive operations. Logs can be viewed at a later time. Disadvantage: Limited by the size of buffer size defined. Logs will be tail dropped as the buffer is filled. Since the messages are sent on an unreliable UDP stream, the Syslog Server should be local the router. Persistent Issue Always use logging buffered for such issues.
Do not send logs to monitor or console as real time output hampers performance. Intermittent Issue: Use Syslog server to capture the outputs since we can not keep the logs in syslog server due to the limitation of buffer size and impact on router's internal memory and CPU due to prolonged debugging.
Also, it is a good idea to have this server local to the router. Regardless of the type of logging being done, always issue the following commands: Router config service timestamps log datetime msec This ensures that the debug output will have millisecond level accuracy. Common Problems - 1. Debug output not visible. Check id debugs are enabled: Router show debug Check the logging level: Router show run section logging Router show log 2.
Debug output is being missed. Always capture debugs in internal buffer. If real time output is captured, output might be missed because of the verbosity of the debugs. Also, capture debugs in logging buffer after entering "term len 0" so that the output does not have multiple annoying "More" statements.
Hope this helps in gaining clarity on debugging process. Thank you for a particularly useful article. It was exactly what I needed when I needed it. Buy or Renew.Save Digg Del. Internetworking Technologies Handbook, 4th Edition. It is used to configure, monitor, and troubleshoot the system. Like a computer, a router has a CPU that varies in performance and capabilities depending on the router platform. The Cisco IOS software running in the router requires the CPU or processor to make routing and bridging decisions, maintain routing tables, and other system management functions.
The CPU must have access to data in memory to make decisions or to get instructions. It is available on a router's processor board. It is read-only, which means that data cannot be written to it. The initial software that runs on a Cisco router is called the bootstrap software and is usually stored in ROM.
The bootstrap software is invoked when the router boots up. Flash memory is most commonly used to store one or more Cisco IOS software images. Configuration files or system information can also be copied to Flash.
On some high-end systems, Flash memory is also used to hold bootstrap software. It is used in PCs to store running applications and data. RAM memory is basically used for all system operational storage requirements. This is the configuration file that IOS reads when the router boots up.
It is extremely fast memory and is persistent across reboots. Although CPU and memory are required components to run IOS, a router must also have various interfaces to allow packet forwarding. Interfaces are input and output connections to the router that carries data that needs to be routed or switched. The most common types of interfaces are Ethernet and serial. Similar to the driver software on a computer with parallel ports and USB ports, IOS has device drivers to support these various interface types.
The console port can be connected to a computer's serial connection to gain terminal access to the router. Most routers also have an auxiliary port that is very similar to the console port, but is typically used for modem connection for remote router management. Example shows the console output of a new Cisco router that has just been started. Notice the processor, interface, and memory information that is listed.
When a new router is first started, IOS runs an autoinstall process wherein the user is prompted to answer a few questions. IOS then configures the system based on the input provided.Q1 Is there anyway to view history logs?
Q2 Is logging a global setting? Q3 When we set the logging console 7, does it means all severity level 0 to 7 will be logged or only severity 7 will be logged? Go to Solution. Again syslog is on by default in ios it can't be disabled but if you don't have logging host set it won't actually do anything.
View solution in original post. Q4 Its on but its not doing anything until you configure the ip address for it to send the information too. Q3 Can I check with you, by setting the severity level, it just means that events that met the severity level will logged accordingly. But how do we specify that we want to capture the occurrence of such events.
In that case, if i want to capture information on what is happening when a packet enter a router. I am trying to ping from R1 to R3, packet is entering into R2 but not coming out of it.
For Q4 is there anyway i can turn off syslog logging without configuring ip address? It seems to be always on even without host ip information. I just done a lab test, it seems like with the 2 debug command on, the router can capture any information that is send to the IPs on its interfaces or replied from the IPs on its interfaces. But it does not capture any information about packets that went through it if it wasn't address to its ips.
R2 has this 2 debug on and its interfaces ips are It is directly connected to Hence I ping from 3. The debug above will not capture anything.
I check my current router ciscoit doesnt support EPC and as it is in a lab environment, they are directly connected to another router and doesn't have switches in between them hence i believe SPAN cant work here as well, as it is meant for switches.
I am just wondering, how do you manage to know what are the functions available for each different kind of routers and their versions.
The quickest way is to probably just check is the syntax available when your in config modebut if you want to know exactly whats available you need to go to your software release for that model on the Cisco website where you would download the software ,below the download the section there are a few buttons you can select documentationcommand linethe docs should appear when you select these in the box giving you full guides.
Buy or Renew. Find A Community. We're here for you! Turn on suggestions. Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type. Showing results for. Search instead for. Did you mean:. Cisco Community : Technology and Support : Networking : Switching : cisco show logs - view history logs. No Inactive Message Discriminator.
Collect Debugs From Wireless LAN Controller (WLC)
Console logging: level debugging, 70 messages logged, xml disabled, filtering disabled Monitor logging: disabled Buffer logging: disabled, xml disabled, filtering disabled Logging Exception size bytes Count and timestamp logging messages: disabled Persistent logging: disabled No active filter modules. ESM: 0 messages dropped Trap logging: level informational, 74 message lines logged Q1 Is there anyway to view history logs? Regards, Noob Solved! Labels: Other Switching.
Accepted Solutions. Mark Malone.This module describes how to configure system message logging on your wireless device in the following sections:. By default, wireless devices send the output from system messages and debug privileged EXEC commands to a logging process.
The logging process controls the distribution of logging messages to various destinations, such as the logging buffer, terminal lines, or a UNIX syslog server, depending on your configuration. The process also sends messages to the console. Note The syslog format is compatible with 4. When the logging process is disabled, messages are sent only to the console.
The messages are sent as they are generated, so message and debug output are interspersed with prompts or output from other commands. Messages are displayed on the console after the process that generated them has finished. You can set the severity level of the messages to control the type of messages displayed on the console and each of the destinations.
You can timestamp log messages or set the syslog source address to enhance real-time debugging and management. You can access logged system messages by using the access point command-line interface CLI or by saving them to a properly configured syslog server. The access point software saves syslog messages in an internal buffer. You can remotely monitor system messages by accessing the access point through Telnet or by viewing the logs on a syslog server. This section describes how to configure system message logging in the following sections:.
Messages are displayed in this format:. The part of the message preceding the percent sign depends on the setting of the service sequence-numbersservice timestamps log datetimeservice timestamps log datetime [ localtime ] [ msec ] [ show-timezone ]or service timestamps log uptime global configuration command.
Stamps log messages with a sequence number only if the service sequence-numbers global configuration command is configured.
Date and time of the message or event. This information appears only if the service timestamps log [ datetime log ] global configuration command is configured. A facility can be a hardware device, a protocol, or a module of the system software. It denotes the source or the cause of the system message. Single-digit code from 0 to 7 that is the severity of the message.
Message logging is enabled by default.Introduction Configuration Overview: Related Information:. Many network administrators overlook the importance of router logs. Logging can use for fault notification, network forensics, and security auditing. Console logging: By default, the router sends all log messages to its console port. Hence only the users that are physically connected to the router console port can view these messages. Terminal logging: It is similar to console logging, but it displays log messages to the router's VTY lines instead.
The router accomplishes this by deleting old messages from the buffer as new messages are added. Syslog Server logging : The router can use syslog to forward log messages to external syslog servers for storage. This type of logging is not enabled by default.
Important Information on Debug Commands
The router does not check if a user is logged into the console port or a device is attached to it; if console logging is enabled, messages are always sent to the console port that can cause CPU load.
To stop the console logging, use the " no logging console" global configuration command. You want your router to record log messages, instead of just displaying them on the console. To use logging buffered configuration command to enable the local storage of router log messages:. Router configure terminal Enter configuration commands, one per line. Router config logging buffered informational Router config end.
Router config logging buffered Router config end. Use the terminal monitor command to enable the displaying of log messages to your VTY:. You want to send log messages to a remote syslog server.
By using this we can send messages to an external device for storing this logs and the storage size does depend on the available disk space of the external syslog server.
This option is not enabled by default. Use the logging source-interface configuration command to specify a particular IP address for syslog messages:. F To display the state of system logging syslog and the contents of the standard system logging message buffer, use the show logging privileged EXEC command. Troubleshooting, Fault Management, and Logging. Configuration Change Notification and Logging.When done, select Apply. Step 3.
Ensure the CLI session does not time out and ends. This depends on the type of connection and is done through these commands. This method sends the debug output to a syslog server. The session form where the debug commands are run must remain open, otherwise the WLC stops sending the debug output to the syslog server.
In order to avoid that the console session ends, enable the desired debugs, unplug the computer from the console port and wait for the data to go to the syslog server.
This way, the console session remains alive. In order to avoid that the console session ends, enable the desired debugs, unplug the computer from the console port and wait for the data to be saved in the local file.
Step 7. Any of the methods generate the same outputs. However, it is important to consider that console outputs display at a much lower speed rate than Telnet or SSH sessions but can provide outputs even after network unreachability. Skip to content Skip to footer. Available Languages. Updated: April 27, Contents Introduction. Step 1. Step 2. Log the output of the WLC to a. Enable the needed debugs i.
Once the desired event has occurred, disable the debugs. Collect the file from the path specified at Step 2. Configure the WLC to send the debug output to a syslog server. Once the desired event has occurred disable the debugs. Collect the file from the syslog server. Configure the WLC to save the debug output to a local file. Collect the information from WLC. Debug File Are you sure you want to start? Was this Document Helpful? Yes No Feedback. Related Cisco Community Discussions.Refer to the appropriate Cisco Debug Command Reference documentation for information on specific debug commands.
The output from debug privileged EXEC commands provides diagnostic information that include a variety of internetworking events relating to protocol status and network activity in general. The information in this document was created from the devices in a specific lab environment.
All of the devices used in this document started with a cleared default configuration. If your network is live, make sure that you understand the potential impact of any command. Use debug commands with caution. In general, it is recommended that these commands only be used under the direction of your router technical support representative when troubleshooting specific problems.
Enabling debugging can disrupt operation of the router when internetworks are experiencing high load conditions. Hence, if logging is enabled, the access server can intermittently freeze as soon as the console port gets overloaded with log messages.
Before you start a debug command, always consider the output that this command will generate and the amount of time this can take. For example, if you have a router with one basic rate interface BRIdebug isdn q probably will not harm the system. But, doing the same debug on an AS with full E1 configuration can probably generate so much input that it may hang and stop responding. Before debugging, look at your CPU load with the show processes cpu command.
Verify that you have ample CPU available before you begin the debugs. For example, if you have a Cisco router with an ATM interface doing bridging then, depending on the amount of subinterfaces configured, restarting the router might use a lot of its CPU.
Starting debugs during such a critical time may cause the CPU utilization to rise dramatically and result in a hang or network connectivity loss. But, in most cases, you can use the no debug all or undebug all commands in order to stop the debugs. Refer to the section Obtaining Debug Outputs for more information on safely using debugs.
Refer to Cisco Technical Tips Conventions for more information on document conventions. In addition to the points mentioned above, make sure you understand the impact of the debugs on the stability of the platform. You should also consider which interface on the router you should connect to. This section has some guidelines. Routers can display debug outputs to various interfaces, including the console, aux, and vty ports. Routers can also log messages to an internal buffer to an external unix syslog server.
Instructions and caveats for each method are discussed below:. If you are connected on the console, under normal configurations, no extra work needs to be done. The debug output should be automatically displayed. But, make sure the logging console level is set as desired and that logging has not been disabled with the no logging console command.