I was having a problem with a router that I'm not sure how's the best way to prevent it from happening again. I have a MC3810 running 12.3, and it provides a PRI and NAT through a T1 data connection.
One of the computers running through the NAT got a virus and started opening up thousands of connections to port 443 per second. This caused the IP Input process to max out the CPU time, and as a side effect VoIP calls couldn't go through.
I fixed the problem with an access list so that port won't be a problem in the future, however, I'm sure at some time some other virus will cause a similar problem with another port.
Is there any way I can force the router to still handle VoIP calls even with a high CPU utilization? I know the IP Input process is obvoisly important for VoIP calls too, but I wonder if there is a way I could give higher preferences to certain types of activity over others.