You're seeing it in "show logging" because that's controlled by "logging buffered [syslog level]". To have it sent to your syslog server, adjust "logging trap [syslog level]".
http://www.cisco.com/univercd/cc/td/doc/product/software/ios11/dbook/dintro.htm
Limiting Messages to a Syslog Server
To limit how many messages are sent to the syslog servers, use the logging trap router configuration command. The full syntax of this command follows:
logging trap level
no logging trap
The logging trap command limits the logging messages sent to syslog servers to messages with a level up to and including the specified level argument. The level argument is one of the keywords listed in Table 1-1.
To send logging messages to a syslog server, specify its host address with the logging command.
The default trap level is informational.
The no logging trap command disables logging to syslog servers.
The current software generates four categories of syslog messages:
Error messages about software or hardware malfunctions, displayed at the errors level.
Interface up/down transitions and system restart messages, displayed at the notification level.
Reload requests and low-process stack messages, displayed at the informational level.
Output from the debug commands, displayed at the debugging level.
