How is your heartbeat configured? We have ours configured
with a crossover cable and as such is not dependent on the
network switching hardware. So our cluster just sits and
waits until people can connect external network
connectivity is lost.

I have had issues with SQL Mail though when connectivity
to the mail server and SQLServer service needs to be
restarted. But this only hangs SQLMail ability to send
mail. SQL seems to work okay other than that.

Our SQL Cluster is inside the internal network and the web
servers are in the DMZ.
~Chris