This depends on what you have in the 6500.
The connection from the 4250-XL is a 1000-SX connection. It requires a multi-mode fiber cable with an MT-RJ connector on one side (the type of connector needed for the 4250-XL ports), and another connector on the other side to connect to your switch.
NOTE: There are 2 ports on the 4250-XL each of which are MTRJ. Some users have confused these 2 MTRJ ports as being a single SC port. Since these are 2 ports you can even connect the 4250-XL to 2 different switches to monitor 2 networks.
The most common type of connector on the 6500 switch is the SC style connector. Most users have a Gig card with GBIC slots. They purchase a 1000-SX GBIC with an SC style connector (WS-G5484). In which case a multi-mode fiber cable with MT-RJ on one side and SC on the other is needed.
There are also Gig modules in the 6500 that have MTRJ style connectors. In which case a multi-mode fiber cable with 2 MTRJ connectors is what you would need.
For more information on the different Gig modules in the 6500 and the types of connectors supported you can refer to:
http://www.cisco.com/en/US/products/hw/switches/ps708/products_data_sheet09186a008014c49f.html
NOTE: The Gig ports on the Sup1A and Sup2 cards are GBIC slots. If you want to use one of these then purchase WS-G5484 (which is a 1000-SX GBIX with a SC style connector) and CAB-MTRJ-SC-MM-1M (which is a 1 Meter multi-mode fiver connector with MTRJ and SC style connectors). CAB-MTRJ-SC-MM-3M is 3 meters, and CAB-MTRJ-SC-MM-5M is 5 meters if you need longer cables.
Other companies also sell fiber cables with these same style connectors.
So you will need to check on your switch module and see what style of connectors it supports in order to determine the type of cable you need.
