VLAN (Virtual LANs) are sometimes difficult to troubleshoot and you face a lot of confusion in isolation a problem especially in an environment where there are alot of VLANs. And this is common in today’s networks, there are hundreds of VLANs on switches and you are required to grasp a knowledge of troubleshooting VLANs in an affective way i-e isolation of problem in minimum ammount of time available. There are some CISCO power point slides which help in gaining and sharpening this knowledge. You can find the slides as follows:

http://rapidshare.com/files/226416774/Troubleshooting_VLANS.ppt