Broadcom network cards, (bce and bge cards), especially those built into Dell hardware, may behave erratically, dropping packets, or causing system crashes especially on amd64.
In /boot/loader.conf.local – Add the following (or create the file if it does not exist):
kern.ipc.nmbclusters=”131072″ hw.bce.tso_enable=0 hw.pci.enable_msix=0
That will increase the amount of network memory buffers, disable TSO directly, and disable msix.