Hi Vishal,
CAM table is a special type of memory used by Cisco switches. In the case of ordinary RAM the IOS uses a memory address to get the data stored at this memory location, while with CAM the IOS does the inverse - it uses the data and the CAM returns the address where the data is stored. Also the CAM is considered to be faster than the RAM since the CAM searches the entire memory in one operation.
The problem with CAM is that it can only do exact matches on ones and zeros (binary CAMs), and here TCAM (Ternary CAM) comes, since it can match a third state which is any. This makes TCAM a very important component of Cisco layer 3 switches and modern routers, since they can store their routing table in the TCAMs, allowing for very fast lookups, which is considerably better than routing tables stored in ordinary RAM.
There is a good explanation of TCAM in the BSCN book (see extract from it in attached file).
PS: check the following guide if you suspect a problem with TCAM on 4500:
http://www.cisco.com/en/US/products/hw/switches/ps663/products_tech_note09186a008054a499.shtml#types
Kind Regards,
Ivan
**Please grade this post if you find it useful.
Kind Regards,
Ivan
