MultiLayerSwitch-CAM/TCAM Flashcards
What does TCAM stand for?
Ternary Content Addressable Memory.
What information does the TCAM table hold?
ACLs, next-hop routes, and QOS info.
What is the TCAM?
TCAM is a memory that stores masks and pattern information for faster L3/L2 lookups. It should match CEF in terms of contents but not possible to verify.
What does CAM stand for?
Content Addressable Memory.
What is CAM?
CAM is specifically used for MAC address lookups where every bit in the lookup key must find an exact match.
What is the default behavior of the switch when no match is found in CAM?
The switch will flood by default if there is no available CAM entry.
What is the default MAC Address Age Timer?
The default *MAC Address Age Timer* is five minutes.
How many CAM tables are on a switch?
One CAM table per VLAN. When a VLAN is created a CAM table is also created.
Where are security and QoS ACLs stored?
TCAM
How often are CAM table entries aged?
300 sec
What are TCAM entries composed of?
value, mask, and result (VMR) combinations
What is the size of a TCAM value?
134 bits, consisting of source and destination addresses and protocol information from the packet or frame
How long are TCAM masks?
134 bits
By default how long are CAM table entries kept before they are deleted?
300 seconds.
What are the name differences between the Layer-3 and Layer-2 forwarding tables?
-Layer-2 is the CAM.-Layer-3 is the FIB.
TCAM entries are organized by which of its three components?
Mask.
In a switch, what is the CAM?
Content-Addressable Memory, or the address table. It holds the MAC, egress port, VLAN ID, and a time stamp.
What are TCAM entries composed of?
-Values, Mask, and Result (VMR) combinations.-Values are 134-bit, containing source and dest IP address and protocol information. -Masks are 134-bit (self explanatory)-Results are numeric values that represent what action to take.
Each TCAM mask can have/has how many values associated with it?
8 Values for each Mask
What two components are part of the TCAM operation?
Feature Manager and Switching Database Manager.
What is an LOU and when is it used?
Logical Operation Unit, used when an ACL line uses a port operator like gt, lt, or range. The Feature Manager uses this to compile the TCAM entry for the ACL.
What happens if a CAM table is full?
A switch will flood all frames like a hub
Where are MAC address Stored?
CAM Table
Define the CAM table.
Content Addressable Memory table, AKA MAC address table.
Define the TCAM table.
Ternary Content Addressable Memory table. Used in L3 switches.
CAM table entries are purged when….
a MAC is seen on a different port
What is the FM?
Feature Manager - after the ACL is created, the FM compiles the ACEs into the table
What are LOU register pairs?
used when ACLs specify port ranges…used by TCAM
