CAM – Content-Addressable Memory
The CAM Table is the basic reference for a switch in terms of frame switching.
Routing a package – Router – Level 3 – Routing table via IP address.
Switching a frame – Switch – Level 2 – Table CAM via MAC address.
It lets you know which MAC address is going to which port.
Don't be confused:
ARP Table – Relationship between an IP address and a MAC address
TABLE CAM – Relationship between a MAC address and a port number!
To view it, use the command:
Switch show mac address-table
This table contains:
– The VLAN-ID;
– The MAC address;
– The port number .
I'm a Switch and I just got a frame from a customer! What am I supposed to do?
– I look in the frame at the destination MAC address.
– I look in my CAM Table and find this: XXXX:XXXX:XXXX via FastEthernet 0/1.
– I know that the address MAC XXXX:XXXX:XXXX is on the port Fa 0/1.
– I transfer this Trame to the FastEthernet 0/1 port!
there is!!!! Touuuuut simply!
But how does this CAM table fill up?
Filling the CAM table
Three ways to fill this CAM table:
A Switch uses a CAM table to distribute the frames it receives only to the recipients concerned.
It will record the source MAC address of all the frames it receives in the CAM table.
By default, all CISCO switches fill their table dynamically.
To disable the automatic filling of your equipment's CAM table, use the following command:
Switch (config) - mac address-table learning vlan
It is possible to make static entries in our table:
Switch (config) - mac address-table static AAAA. Yyyy. AAAA vlan 10 Fe0/1 interface
Solution to be implemented with caution and only when you have no other choice.
It is possible to secure access from a port to one or more MAC addresses.
(See article on Port-Security)
Adding MAC security to a port will create a static entry into the CAM table. In order to view the MAC addresses entered with this method, you can use the following Show command:
Switch show mac address-table secure
– 300s for a Switch;
– 14,400s for a Router.
To change this expiration time:
Switch (config) - mac address-table aging-time 300
Search for a MAC address on a LAN network
Hoping this article has been helpful to you! Don't hesitate to let me know!!
This site has other network items, take the opportunity to browse the menu bar!