350-401 · Question #1149
What is a difference between TCAM and the MAC address table?
The correct answer is C. The MAC address table is contained in CAM. ACL and QoS information is stored in TCAM.. The MAC address table is stored in Content Addressable Memory (CAM), whereas Ternary Content Addressable Memory (TCAM) stores more complex information such as Access Control Lists (ACLs) and Quality of Service (QoS) rules.
Question
What is a difference between TCAM and the MAC address table?
Options
- AThe MAC address table supports partial matches. TCAM requires an exact match.
- BTCAM is used to make Layer 2 forwarding decisions. CAM is used to build routing tables.
- CThe MAC address table is contained in CAM. ACL and QoS information is stored in TCAM.
- DRouter prefix lookups happens in CAM. MAC address table lookups happen in TCAM.
How the community answered
(38 responses)- A3% (1)
- B3% (1)
- C87% (33)
- D8% (3)
Why each option
The MAC address table is stored in Content Addressable Memory (CAM), whereas Ternary Content Addressable Memory (TCAM) stores more complex information such as Access Control Lists (ACLs) and Quality of Service (QoS) rules.
TCAM supports partial matches (wildcarding) as well as exact matches, while the MAC address table (in CAM) primarily requires an exact match for Layer 2 forwarding decisions. The statement reverses this characteristic.
TCAM is used for many forwarding decisions, including Layer 3 routing table lookups (longest prefix match) and ACLs, not just Layer 2 forwarding. CAM is primarily used for the MAC address table for Layer 2 forwarding decisions.
The MAC address table, crucial for Layer 2 forwarding, is stored in CAM (Content Addressable Memory), which supports exact match lookups. TCAM (Ternary Content Addressable Memory) is more complex, allowing for exact, prefix, or wildcard matches, making it ideal for storing and quickly searching complex rules like ACLs, QoS policies, and longest prefix match routing entries.
Router prefix lookups (Layer 3 routing decisions) often happen in TCAM for fast longest prefix matching, while MAC address table lookups (Layer 2 forwarding decisions) happen in CAM. The statement reverses this.
Concept tested: CAM vs TCAM functions
Source: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/12-2SX/configuration/guide/cfg_n_vol1/sw_qos.html
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