Cam table ,Tcam table and SDM template

Mac address table (CAM)

 In switches Content Addressable Memory (CAM) is used for building and lookup of mac address table that enables L2 forwarding decisions. Besides Longest-Prefix Matching,TCAM in today's routers and multilayer Switch devices are used to store ACL, QoS and other things from upper-layer processing.

The MAC address table is contained in CAM ACL and QoS information is stored in TCAM

When using Ternary Content Addressable Memory (TCAM) inside routers it's used for faster address lookup that enables fast routing. 

We need to configure our switches:

Let's figure out our basic topology:

So in real life we usually have this mess:

Red cable is the crossover cable The one for the 2 switches)



We can check our Mac address table:
show mac-adress table

We could see the mac address of the switch and the VOIP phone
We could see the aging time..

We are checking on the Mac address of the switches

 We click on that specific interface and we see that it's an uplink: Our switch has devices connected to the F0/1 port

 We don't want our switch to learn to many new mac address specially in a large environment.If the mac address table is filled up and there is a  new device , it won't be learn, if a new frame comes  to the switch the switch will flood that frame throught all the other port  besides where the port resides because it going to an unknown Mac adress


We need to see the mac-address aging-time

show mac-address aging-time

We saw the aging time: 300 seconds (5 minutes) by default. We wanted to change it, so it wont get flushed:3600 (1 hour).

We configures: mac-adress aging-time 3600



To see the CamTable size use show Mac adress-table count 

Layer 2 switches makes decision based on Mac address

• Ternary CAM Is a layer 3 version of the CAM tale

•  Uses ASICS  (Application specific Integrated switches) , a high speed circuit for specific purpose,with CAM memory to accomplish QOS, ACLs and routing .
• ASICS, a high speed circuit  use for example in frame forwarding , sometime is called wire speed
• A layer 3 switch is going to follow CAM information, TCAM information and can forward  based on destination of IP address 

You can verify  Tcam utilization with this command:
show platform tcam utilization

Switches can have multiple TCAMS: one for outbound ACLS, one for inbound for ACLS, one  for QOS

A lawyer 3 switch can make forwarding based on an IP address (FIB) table ..Forwarding Information Based

(Switch Database Management) It's a collection of settings  that can allocate a switch resources (Ex. TCAM resources)  in different ways depending of the role of the switch.
You can check with the command
#Show sdm prefer

We see this is the default template of our switch.We can see that this interface support 8 routed interfaces and 1000 Vlans

but we can see different templates as well using the command sdm prefer in configuration mode
#conf t
#sdm prefer ?

 

We see different templates: access, extended-match, routing and Vlan
 For example we can use access in case we will use as an access switch, can support many vlan but no much routing

 We are using the switch 3550, and this particular switch supports IPV6.Others switches don't support it..And you need to enable it on the sdm

 You can see your resources with :
# show platform tcam utilization