difference between switches.

Unanswered Question
Jan 30th, 2008

Hi folks,

Can any body give full info. about difference between L2 & L3 switches.



I have this problem too.
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Edison Ortiz Wed, 01/30/2008 - 09:21

Layer2 switches allows you to connect end devices and create multiple Layer2 Vlans on its database.

For end devices to communicate from one Vlan to another, they need a Layer3 device. When using Layer2 switches, you need an external Layer3 device (router) for this task.

While if you elected to go with the Layer3 switch, the router function is done internally and you don't need an external router.




Joseph W. Doherty Wed, 01/30/2008 - 17:23

L2 switches deals with L2 frames (e.g. Ethernet frame with MAC addresses).

L3 switches deal with L3 packets (e.g. IP packets and IP addresses).

L2 switches usually learn the frame's outgoing port by seeing earlier frames on the same port with the destination address. If destination address has not yet been seen, L2 switches usually flood the frame to all other ports except the one it arrived on.

L3 switches usually learn the packet's outgoing port by manual configuration (e.g. static route), from a dynamic routing protocol (e.g. RIP/OSPF/EIGRP/BGP), or by known connected destination address blocks (e.g. interface addresses with subnet masks). If the destination address is unknown, normally the packet will be discarded unless a default path has been defined.

A L2 switch is also known as a multiport bridge.

A L3 switch is also known as a multilayer switch. (It often can function as a L2 switch too.)

A L2 swich is commonly used in place of a hub.

A L3 switch is commonly used in place of a router.

The difference between a L3 switch and a router is the former is often "faster" but the latter is often feature "richer". So, L3 switches are common within LANs and routers common for within WANs. (Today the two often overlap.)


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