Online CCNP Certification Training: Switch Port Configuration
Let us begin with the objectives of the lesson in the next slide.
Explain the methods to perform Multilayer Switch Forwarding
Identify the fields involved in Layer 3 routing packet rewriting
Describe the types of switch interfaces in Layer 2 and 3
Configure speed and duplex
Explain err-disabled interfaces and re-enable them
Configure Miscellaneous Switch commands
Let us begin the discussion with Multilayer Switch Forwarding methods.
Multilayer Switch Forwarding Methods
Route caching is no longer the default forwarding method for IOS Catalyst switches. However, this is still used to gather traffic flow information, so it is important to understand how the processing occurs.
Let us look at Cisco Express Forwarding, Cisco’s topology-based switching, and how it works.
Cisco Express Forwarding
CEF uses two areas in memory Content Addressable Memory (CAM) and Ternary Content Addressable Memory (TCAM). Let us look at them in the next slide.
Content Addressable Memory and Ternary Content Addressable Memory
Ternary Content Addressable Memory or TCAM is different. TCAM processing returns three values: 0, 1, or don’t care. This range of results is required for the more complex matching involved in ACLs, QoS, and routing tables. For example, a lookup can be initiated for longest matches, first matches, or exact matches. Each TCAM entry consists of Value, Mask, and Result combinations.
There is a special area in the TCAM called the LOU. If an ACL entry concerns port number calculations as shown in the slide, an LOU register entry is created that includes both the operator and operand involved. The TCAM has a limited number of LOUs.
Let us look at the two tables used by the TCAM.
About the On-Demand Webinar
About the Webinar