Does normal mode make port go into error-disable mode, Leo.
Both modes can result in error-disable, but the mechanisms are different:
"In normal mode, a protocol determination at the end of the detection process is always based on information received in UDLD messages: whether it's the information about the exchange of proper neighbor identifications or the information about the absence of such proper identifications. Hence, albeit bound by a timer, normal mode determinations are always based on gleaned information, and as such are "event-based". If no such information can be obtained (e.g., because of a bidirectional loss of connectivity), UDLD follows a conservative approach based on the considerations in Section 3 and deems a port to be in "undetermined" state. In other words, normal mode will shut down a port only if it can explicitly determine that the associated link is faulty for an extended period of time."
"In contrast, in aggressive mode, UDLD will also shut down a port if it loses bidirectional connectivity with the neighbor for the same extended period of time mentioned above and subsequently fails repeated last-resort attempts to re-establish communication with the other end of the link. This mode of operation assumes that loss of communication with the neighbor is a meaningful network event in itself and is a symptom of a serious connectivity problem. Because this type of detection can be event-less, and lack of information cannot always be associated to an actual malfunction of the link, this mode is optional and is recommended only in certain scenarios (typically only on point-to-point links where no communication failure between two neighbors is admissible)."
Hope that helps
Rolf
