logging buffered enables Cisco IOS to store Syslog messages in the device’s RAM, preserving a short historical record for later review instead of limiting visibility to real-time output. section 7.1.3
Configure and interpret the buffer with these operational facts:
- Use logging buffered [bytes] to enable buffering and optionally allocate a specific buffer size; the command is enabled by default. section 7.1.3
- The buffer uses FIFO behavior: after it fills, new messages replace the oldest messages. section 7.1.3
- Add a severity value or keyword to store only that severity and numerically lower, more severe events. section 7.2.2
- Check stored messages, buffer size, and logging settings with show logging; check available memory before increasing capacity with show memory. section 7.1.3
Configure and verify a larger buffer
Device(config)# logging buffered 102400 warnings Device# show logging Buffer logging: level warnings Log Buffer (102400 bytes): The configuration allocates 102,400 bytes and retains warning-level events plus all more severe events. The exact default buffer size depends on the device model. section 7.1.3 section 7.2.2
SW1# show logging
. . .
Console logging: level debugging, 5014 messages #1
logged, xml disabled, filtering disabled #1
Monitor logging: level debugging, 1080 messages #1
logged, xml disabled, filtering disabled #1
Buffer logging: level debugging, 4500 messages #1
logged, xml disabled, filtering disabled #1
. . .
Trap logging: level informational, 18 message lines logged
Logging Source-Interface: VRF Name:
Log Buffer (4096 bytes): #2
. . .
Sep 18 10:35:06.528: %SEC_LOGIN-5-LOGIN_SUCCESS: Login
Success [user: jeremy] [Source: 192.168.1.224]
[localport: 22] at 19:35:06 JST Mon Sep 18 2023
Sep 18 10:35:14.539: %SYS-5-CONFIG_I: Configured from #3
console by jeremy on vty0 (192.168.1.224) #3
#1 Console, monitor (VTY line), and buffer logging are enabled by default.
#2 The logging buffer is 4,096 bytes in size.
#3 The most recent messages are shown at the bottom of the output.
Use the annotated show logging output to identify whether buffer logging is enabled, which severity threshold applies, the allocated size, and recent messages. section 7.1.3
