The h1sush2a computer was shutdown to allow a DAC card (D0) to be replaced in the I/O chassis, due to reports of a stuck voltage.  See alog 18543.

It was not possible to log in to this computer remotely, as it was not accepting new connections due to a "nf_conntrack: table full" error viewable on the console.  I was able to shut the computer down in an orderly manner from the console.  We have not encountered the nf_conntrack error in many months, but it appears when there's too many network connections being made.

The stuck voltage on D0 disappeared after the card was replaced and the computer restarted.