Some routers support detailed logging via Syslog. Syslog is an industry standard protocol used for capturing log information for devices on a network, usually via UDP Port 514.

Syslog support is included in Unix and Linux based systems, but is not included in Windows. However, there are third-party applications available to add this capability to your system.  
 

• Kiwi [Win95,98,NT, 2000]
  "Basic" features are free, more advanced features require registration.
  http://www.kiwi-enterprises.com/
  Supports multiple TCP syslog connections from many vendors including Allied Telesyn, 3com, Cisco and extreme.
  Download
   

• 3COM has a free syslog daemon
  ftp://ftp.3com.com/pub/utilbin/win32/3CSyslog.zip



• TriAction Syslog Daemon
  30 day free trial
  http://www.triaction.nl/Products/SyslogDaemon.asp
  Has rule engine for filtering and rerouting of messages. Can also react to events and trigger or execute an external program.