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when will will use layer 3 switch?

Dear Sir,

I am going to implement a big network.  I have bought 48 port LinkSys Layer 2 switch 10/100 with 4 Giga Port of 6 Nos.

The usage and users will be Windows 2003 and Client will be Windows XP.  Windows 2003 will act as a file server.

I would like to know, for this network, is it required Layer 3 Switch?

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If you are using just to connect to LAN ( no traffic outside the lan or outsite your network) then you won't need layer3 switch.

 If you want to transfer some information outsite your network then you will need a router. Layer3 switch performs a layer 2 function at layer 3. That is, it will route the First packet depending on the routing table.. rest packet for that particulat destination are just switched. thus reducing very much of processor load.

 Peace and Health
Ravi Simpi
If you are shopping for a Layer 3 switch, first see if the switch meets all, or at least most, of the following criteria:

Multiprotocol support. IP switching and routing isn’t the only function that Layer 3 switches perform. New models can also handle protocols such as Novell IPX, AppleTalk, XNS and IBM SNA.

Peer router support. Because Layer 3 switches support current routing protocols, they should participate as peers of software-based routers in IP or other networks.

Multicast control. This is the ability to broadcast multimedia traffic such as streaming video.

Management support. Simple Network Management Protocols let diverse network gear communicate. The various levels of advanced RMON, or remote monitoring, protocols give network managers the ability to manage their Layer 3 switches remotely from a central console along with other network equipment.

Spanning tree support. The industry-standard Institute of Electrical and Electronics Engineers 802.1D spanning tree protocol protects against network loops and provides redundant network paths.

Port trunking. Port trunking sets backbone links by treating multiple parallel links as a one backbone pipe. Network redundancy is thus provided, as traffic on any failed link automatically switches to other links.

VLAN support. Virtual LANs allow PCs, servers and other network resources to be organized into logical domains so that only devices within the same domain can communicate with each other. The IEEE 802.1Q standard enables switches to automatically learn VLAN configurations.

Flow control. Flow control is a feature that eliminates dropped packets on congested ports. The IEEE 802.3x standard supports flow control in full-duplex situations.

Layer 4 support. The newest category of Layer 3 switches includes support for Layers 4 and above of the Open Systems Interconnection model. This ensures a full measure of traffic control and contributes to the ability of the switches to provide advanced quality-of-service support.

Fault tolerance. This may include dual CPUs in some cases, but it may also mean dual or backup power supplies and redundant cooling fans.

Hot-swappable. Interface modules holding various port configurations and other components may be swapped without shutting down the switch.
Hello liji77,

The decission about using a Layer3 switch instead a Layer2 switch is usually not related to the size of the network, but to the specific needs it has.

The difference between a layer 2 and a Layer 3 switch is basically that the Layer 3 has integrated high speed routing capabilities, so, anytime you need to divide the traffic in different networks (or vlans), and you still need intensive traffic between the different networks, the recommended solution will be a Layer 3 switch.

In case you want just to connect the computers without special network subdivision, a simple Layer 2 switch would be enough.

For a high performance high speed solution in your network, you could use a layer 3 switch, divide the network in two VLANs, one for the clients, another one for the server and route between them using the routing capabilities. This will isolate the server from the inter-client traffic and broadcasts, but depending on your traffic model could be not needed.

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