Hello Son,
When you speak about CAM, you speak about the technical characteristic of the memory and not about its contents. While it is often implied that the CAM table is the same as MAC table, this is a gross misunderstanding. The CAM is a specific type of hardware memory with a unique principle of operation and usage while MAC table is simply a data structure. The CAM can store MAC table and many other kinds of data - it is not limited to pure MAC addresses.
- CAM table (or MAC table) was stored in DRAM of routers (or switches)
This is not a precise statement. A CAM can not be stored in DRAM - just like, for example, a hard disk drive can not be stored in DRAM. What was stored in DRAM was the MAC table.
Software-based MAC address table is indeed located in DRAM in lower-end routers and software bridges.
- Modern routers or switches use a seperate memory to store CAM table. This memory can be referred to as CAM memory
More precisely, modern switches use a separate memory, the CAM, to store the MAC table.
Regarding routers - not all routers even today use CAM. In fact, to my best knowledge, none of the ISR or ISR G2 routers have built-in CAM. The CAM and TCAM is quite a distinctive feature of multilayer switches.
It should also be said that even if a device has a CAM to store, for example, the MAC table, this table is often also stored in the DRAM, so it is actually present twice in the switch - one copy in the DRAM, second copy in the CAM. The CAM contents have to be programmed based on input data, and these input data are first stored in the DRAM. Lookups are performed only in the CAM but the data from which the CAM contents are compiled are also stored in the DRAM.
- TCAM memory is again different from CAM and DRAM
This is true.
-> So, it is possible for a router or switch to have all 3 seperate physical memories at once????
Yes, absolutely.
Best regards,
Peter
