The Cisco Catalyst 2950 switch is supported by either the standard software image (SI) or the enhanced software image (EI). For more information on which hardware (Cisco Catalyst 2950, 2955, 2940) supports which software image, refer to Release Notes for the Catalyst 2955, Catalyst 2950, and Catalyst 2940 Switches, Cisco IOS Release 12.1(22)EA5 and Later.
Cisco Catalyst 2950 switches that run the standard SI support 64 VLANs. The Cisco Catalyst 2950SX-24 supports only 64 VLANS. When the server tries to pass more than 64 VLANs on an SI release, it causes unexpected behavior.
For more information on this issue, refer to Configuring VLANs.