The number of vlans allowed on a Cisco switch are generally higher than almost anyone except an ISP or massive company would ever need.
The cisco switches support vlan ID numbers 1-4094. The number you can actually USE is more limited, depending on the switch. The 3750 line should let you define 1024 actual vlans simultaneously on a switch.
http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps7077/prod_qas0900aecd805bbea5.html
Layer 2 Features
The following section explains the Layer 2 features for the Cisco Catalyst 3750-E. They include Layer 2 forwarding, MAC learning, Spanning Tree Protocol, and so on.
Q. How many EtherChannel groups are supported in a Cisco Catalyst 3750-E?
A. Forty Eight groups are supported, and each group can have up to 8 ports with the same speed, duplex mode, native VLAN, VLAN range, trunking status, and type.
Q. How many Spanning Tree Protocol instances are supported on the Cisco Catalyst 3750-E?
A. 128 Spanning-Tree Protocol instances, 1024 VLANS, 63 bridge groups and up to 4000 user-configurable VLAN IDs.
Q. Is Network Address Translation (NAT) supported?
A. No, there are no plans to support NAT.
Q. Is the full private VLAN feature supported?
A. Yes, it is supported in the IP Services feature set. In the IP Base feature set the private VLAN edge (protected port) feature is supported. In addition, the local proxy ARP feature is supported, and thus no external router is required.
As far as interfaces go, you can trunk as many vlans as you have defined, and you can put them on any interface you want. You can choose on a per-port basis which vlans are access, voice, trunked, etc. The only real limitation is the number of switch ports you have, the range of allowable vlans (1-4000 essentially) and that you can only define about 1000 on the switch itself.
Odds are you'll never need anywhere near that many, since you can have 1000 vlans and only have 24 or 48 ports to put them in!
Andy
