Long router ACLS can cause significant CPU consumption. This will likely be traffic dependent. PIX devices deal better with a large shun list. If you are going to greatly raise the shun limit, I would highly recommend using a PIX.
Minimal monitoring capabilities can be found in the Security Monitor->Monitor->Connections tab. However, I do not beleive that any active notification can be configured for status changes there. Also, this does not cover all possible ways that a sen...