What is the actual difference between TCAM and MAC address table.

[AZR]

Hello Everyone,

                           Hope you all are well. I am trying to get by brains around this topic but unable to completely understand how and what happens in TCAM and CAM. I went through the following docs and still not sure about few things. Please share your insights on this.

https://community.cisco.com/t5/networking-knowledge-base/cam-content-addressable-memory-vs-tcam-ternary-content/ta-p/3107938

Thanks

AZR

[MHM Cisco World]

Both are memory allocation i.e. both are HW
CAM use to save the MAC address 
TCAM use for what?
some not all process in SW can be done by SW (CPU) or by HW (TCAM)
for example if you bay Christmas tree lamp, which change it color each time, this circuit not have CPU it have HW program for special purpose thing (change color of lamp).
same in SW it have HW program for special purpose thing like QoS, some ACL...
this make SW process the frame in HW and only few frame go to CPU.

[David Ruess]

Hello,

Try this link:

Difference between TCAM and CAM - GeeksforGeeks

-David

[Jon Marshall]

What things are you still not sure about ? 

Jon

[Joseph W. Doherty]

As @Jon Marshall asks, what are you unsure about?

Your original reference seems pretty clear, and the reference @David Ruess provides is pretty much explaining the same.  Are you sill unsure about CAM vs. TCAM after reading David's reference?

BTW, I see in your posting's title, you ask about the difference between TCAM and MAC address table.  The former is a technology (and so is CAM, or even RAM) that might be used to support a switch's MAC address table.

[AZR]

Hy @Jon Marshall and @Joseph W. Doherty 

                        Thanks for responding. From the article does it mean that TCAM is completely Layer 3 specific and CAM Layer 2 specific. So CAM has MAC table and layer 2 lookup related information and TCAM has all the routing table lookup related information?

Thanks

AZR

[Joseph W. Doherty]

Not exactly.

CAM vs. TCAM depends on what you're trying to match.  That said, MAC only needs CAM, but it could use TCAM.  Something like route prefix lookup would often need TCAM.

However something like a simple L3 ACL ACE, that permits or denies based on a host address could also use CAM.

TCAM is useful for "wildcard" matching.  So it could be used to match against all Ethernet multicast MACs, L2.

[AZR]

By your response it is safe to say that MAC address table is not contained or bounded to CAM only, it can some time use TCAM as well? and Router prefix lookups happens only in TCAM and MAC address lookups happen in CAM.

AZR

[Joseph W. Doherty]

Regarding whether to use CAM or TCAM for MAC table lookups, depends on the design of the switch.

If the switch is just a "dumb" L2 switch, it likely would only use CAM for MAC table lookups.

If the switch is a "smart" L2 switch or a L3 switch, it would likely have TCAM, and likely would use that for MAC table lookups too (to avoid the issue of providing CAM in addition to TCAM).

[MHM Cisco World]