only 50%?
Last I heard Cisco's market share was up in the 70-75% range, with HP about 10-15% and most of the rest of the vendors sub 5% each. I seem to recall Juniper being in the 6% range (at one point in the past year or so anyway), Extreme was in the ~3% range until they bought Entarasys and doubled their market share to 6% (they were something like within 0.2% of Juniper's market share at the time they said). Brocade was in the 3-4% range as well, not sure on Arista.
If Cisco is down to 50% that is quite a hit.