UDLD Aggressive is not enabled by default.
by David Sudjiman ~ August 12th, 2008. Filed under: Cisco.I thought I knew enough about UDLD. Petr Lapukhov from Internetwork Expert writes a good explanation about UDLD Modes of Operation. From this writing I found out that udld aggressive is not enabled by default.
Also, based on Cisco Documentation about UDLD Aggressive Mode, what’s on by default is udld enable which will not bring the link down yet only mark the port as Undertermined.