Hi,
first you will need to make sure that you actually log events with a certain severity. Link up/down events have the format LINK-3-UPDOWN or LINEPROTO-5-UPDOWN, i.e.
00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to up
00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to down
Make sure your Cisco IOS devices have at least the following config:
logging trap informational
logging host YOUR.SYSLOG.SERVER.IP
logging event trunk-status global
logging event link-status global
!
interface ra Gi1/0/1 - 52
logging event trunk-status
logging event spanning-tree
logging event status
!
This ensures that all link up/down events are logged. Not all of these commands may work for your device however, but they should be enough to get link up/down events logged.
If this didn't help please try to search for the following: eventtype="cisco_ios-port_down" OR eventtype="cisco_ios-port_up"
Do you get any results? If so, please post them here so that I can see if everything was matched correctly.
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