Many network administrators overlook the importance of router logs. Logging can use for fault notification, network forensics, and security auditing.
Cisco routers log messages can handle in five different ways:
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. This is not enabled by default Buffered logging:This type of logging uses router's RAM for storing log messages. buffer has a fixed size to ensure that the log will not deplete valuable system memory. 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.
SNMP trap logging:The router is able to use SNMP traps to send log messages to an external SNMP server.
Sample router log messages:
System shutting down due to missing fan tray
Temperature limit exceeded
Memory allocation failures
Interface Up/Down messages
Configuration file written to server, via SNMP request
Line protocol Up/Down
Access-list violation logging
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 might want to limit the amount of messages sent to the console with the "logging console level" configuration command (for example, logging console Informational).
B) Buffered logging:
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. End with CNTL/Z. Router(config)#logging buffered informational Router(config)#end
You can also Set the Log Size on router.
Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#logging buffered 64000 Router(config)#end
C) Terminal logging:You want the router to display log messages to your VTY session in real time.Use the terminal monitor command to enable the displaying of log messages to your VTY:
Router#terminal monitor Router#
To disable logging to your VTY session, use the following command:
Router#terminal no monitor Router#
D) Syslog Server logging:
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.
If you have any syslog server please find the below simple config.
Router(config#logging host x.x.x.x
Router(config)#logging traps (i.e 0 1 2 3 4 5 .. according to your requirement)
before enabling logging be sure that your router is properly configure to collect proper time from any NTP server or manually configure to get time
Command to set time manually on router is (set clock) or to use ntp server use “ntp server x.x.x.x” to sync clock to router.
Use the logging source-interface configuration command to specify a particular IP address for syslog messages:
Router(config)#logging source-interface Loopback0
E) Clearing the Router's Log
Use the clear logging command to clear the router's internal log buffer:
Hello all, I have R1 and R2, each are connected through the public internet by using IPsec tunnel, and on this R2, i have one management interface: INT F0/0.99 10.10.99.3 /24 I would like to telnet from R1 LAN to the interface on R2, but un...
What is the difference between "isis three-way-handshake ietf" and "isis three-way-handshake cisco" ? When I did packet capture with isis three-way-handshake ietf there were extended local circuit ID , Neighbor system-ID and neighbor...
We have a hub and spoke router but connection should work only when primary connection at the site fails however I run to a issue that from hub we are fording the traffic via the tunnel instead via the private connection.As checked between working and non...
Hello,I hope you and your loved ones are safe and healthy. I am want to integrate a Cisco Integrated Service Router "RV-345" into my network & use VLAN to segregate traffic. Current setup:Netgear Wi-Fi router is the only component carrying o...
I am now working on Catalyst 9200L-24T-4G and 48T-4G switches. When I tried to configure trunk ports, the option switchport encapsulation dot1q/isl doesn't exist. Then I looked for data sheets and there isn't any mention about ISL, but...