Cisco Systems 4500 manual Over-subscription

Chapter 1 Product Overview

System Architecture

Figure 1-23	Switching Traffic Flow
		MUX	2 Gigabit Ethernet
	6 Gbps up / 6 Gbps down		uplinks
			24 Gbps
MUX	1000BASE-T 8:1
	(oversubscribed)		(Supervisor Engine)
		Clock
	6 Gbps up / 6 Gbps down

1000BASE-T 1:1

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Frames flow into the switch through interfaces on the switching modules. Each switching module connects to a mux/buffer on the backplane that supports a connection of up to 6 Gbps up (Tx) to the supervisor engine and 6 Gbps from (Rx) the supervisor engine. When a frame reaches the supervisor engine, it is examined and either sent out of an interface in one of the other slots, or out of the uplink on the supervisor engine.

Over-subscription

Switching modules that have 24 or 48 Gigabit Ethernet (1000BASE-T) ports over-subscribe on a Catalyst 4500 switch by grouping the ports with an additional mux/buffer on the switching module, which creates a single, nonblocking, full-duplex Gigabit Ethernet connection to the internal switch fabric. For each group of ports, frames received are buffered and sent to the common Gigabit

Catalyst 4500 Series Switches Installation Guide

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