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Difference Between L3 & L2 Switches

By sree_cb ·
Hi Techies.

Please give me the differneces of Layer-3 & Layer-2 Switches. Pls Help..


thanks & reg'ds

Sree

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by baldeep193 In reply to Difference Between L3 & L ...

layer 2 is for peer to peer communication,
layer 3 is for process to process communication.layer 2 do the routing function with the mac address(ie peer to peer delivery) but laywr 3 do the routing function with the ip address(process to process delivery)

There is only one big diffrence between layer 2 and layer 3 swithces is that we are able to do routing in interanetwork with Layer 3 swithces which is not possible to do with layer 2.

Layer 2 switch has multi collision and single broadcast domain whereas Layer 3 switch has multi collision and multi broadcast domain.

L2 - No Routing, no vlans property.
L3 - Routing and vlans
It means that in Layer 2 switch only one VLAN is active at a time where as in L3 switch we can use as much of VLAN we want.As routing is not possible in L2 switch, we need router for the communication between two or more VLANs but in L3 switch router is not required for the inter VLAN communication.It is the main reason for the use of L3 switch others are secondary reasons.

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by nishitsarkar21 In reply to Difference Between L3 & L ...

Please provide me the perticular
Thanks
Nihsit

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by ashishnirman In reply to Difference Between L3 & L ...

Generally, Layer 3 switches are faster than routers, but they usually lack some of the advanced functionalities of routers.

Specifically, a router is a device that routes the packets to their destination. What this means is that a router analyzes the Layer 3 destination address of every packet, and devises the best next hop for it. This process takes time, and hence every packet encounters some delay because of this.

In a Layer 3 switch, on the other hand, whenever a routing table searches for any specific destination, a cache entry is made in a fast memory. This cache entry contains the source-destination pair and next hop address. Once this cache entry is in place, the next packet with the same source and destination pair does not have to go through the entire process of searching the routing table. Next hop information is directly picked up from the cache. That's why it is called route once switch many. This way, a Layer 3 switch can route packets much faster than the router.

Having explained the mechanism of both a router and a Layer 3 switch, let me also tell you that router has some advanced routing functionality, which Layer 3 switches lack. Layer 3 switches are primarily used in the LAN environment, where you need routing. Routers are used in the WAN environment. These days lots of people have started using layer 3 switches in WAN environment, like MPLS.

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by ashishnirman In reply to Difference Between L3 & L ...

There is only one big difference between the Layer-2 and Layer-3 switches is that we are able to do routing in interne work with layer-3 switches which is not possible to do with layer-3. Cisco 2950 catalyst switch is the example.
Layer 2 switch is for peer to peer communication and Layer-3 is for Process to Process communication.

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by kamran In reply to Difference Between L3 & L ...

hi,
layer 2 switch is a peer to peer communication. layer 3 switch is a process to process communication.
Layer 2 switch: 2950, 1900
layer 3 switch: 4503, 5500

on layer 2 in the header portion(H2) contains source and destination physical addresses...(means all the computers which are in the same network can communicate.......)

while on layer 3 in the header portion(H3) contains logical ip of the source and in the destination portion it contains logical ip of gateway of that(of source) network. and then in the second pass in H3 it contains in the source portion address of the gateway and in the destination portion address of the real destination.( packet can be trasferred though source and the destination are of the different networks)

source 192.168.0.12 subnet255.255.255.0 (here n/w id =192.168.0.0.0)

destination 100.100.100.13 subnet 255.255.255.0 (here n/w id =100.100.0.0)

so with layer 3 switch

pass1----source(192.168.0.12) to gateway(192.168.0.1)

pass2----gateway(100.100.100.1) to destination(100.100.100.13)

where gateway contains both ip addresses of both the networks.

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