GigaStack GBIC is a versatile, low-cost, Gigabit Ethernet stacking GBIC that offers high-speed interconnectivity between Catalyst 3500 series XL and Gigabit Ethernet-enabled Catalyst 2900 series XL switches. The GigaStack GBIC is ideal for performance- and cost-conscious customers who require an independent stack bus to interconnect multiple Catalyst 3500 series XL and Gigabit Ethernet-enabled Catalyst 2900 XL switches.