Arista Networks (ANET) shares tumbled in extended trading Thursday as the company reported shrinking margins, despite profits that topped Wall Street’s expectations. The cloud networking giant saw third-quarter revenue grow 7% year-over-year to $1.81 billion, above the analyst consensus from Visible Alpha. Net income came in at $747.9 million or $2.33 per share, up from $545.3 million or $1.72 per share a year earlier and above projections. However, Arista's gross margin in the third quarter was 64.2%, dow ...