Switches:How many layer?

from my knowledge, there are layer 2 and layer 3 switch
layer 2 for switching and layer 3 for routing..
is that true?
are there any layer 1 or layer 4 switches?

All switches work at Layer 1 as well as any other layers because Layer 1 is the physical layer, so it relates to the physical and electrical characteristics of the network interfaces on the switch. Layer 2 is the 'Ethernet' layer, so this is where switches normally work, looking at MAC addresses and forwarding them to the correct port. Layer 3 is to do with network addressing so if your switch handles VLANs and can route between them then it must work at Layer 3 also. Remember each layer is just a way of grouping together a set of things that have to happen during the communications process, and the numbering of the layers shows the order in which they get done. So when manufacturers talk about a Layer 3 switch they're just saying that it incorporates functions that are explained by layer 3 of the model

Hubs work at layer 1 being that they don't do anything except distribute electrical signals.
Also, NAT routers work at OSI layer 4. Because that they can read and change port numbers.
And if it anything be accessed by a web interface or telnet it actully works at layer 7, but not the routing function itself.

Right?

You even get content switches which work all the way up to layer7.. for example they can understand an HTTP request and 'switch' it to the right server..

Chris played with a 5000 series content switch I think.

To be specific to apit "Yes"

On the other hand I feel the need to rant a little:

To best understand multilayer switching check out CCNP 3. Don't be surprised when you find it is titled "Multilayer Switching". I really don’t mean to say that your question and the following answers are trivial. But you should realize that this is an in depth subject that requires a substantial background in OSI, TCP/IP, routing, and switching. The best source for a copy of Multilayer Switching is Ciscopress.com.

A little more ranting:

The more I see on this site the more I see a need for people to attend a Cisco Academy (one that offers CCNP courses). While a lot of the basic concepts (CCNA) can be learned by self-motivation and determination I am convinced the best (most efficient) way to learn the advanced concepts of networking is to attend an Academy that offers the CCNP courses.

On the other hand five to seven years of experience could provide the same education that a two-year technical institute that offers CCNP courses could offer. The choice is yours.

OK one last rant:

Maybe I am biased because I am aware of an Institute that provides Windows server (always the most recent), Unix, Linux, Novell, iSeries, AS400, and CCNP as part (note that is just part) of its Networking AAS degree. Check out lakeareatech.edu.

tq all for your answer..
one friend's of mine said that core switch sit at Layer 4..is that true?

Layer 3 is to do with network addressing so if your switch handles VLANs and can route between them then it must work at Layer 3 also.

i've installed Nortel switches(baystack 470 24T) and it's have vlan function on it..
i've configured 5 vlan on it..
from manual that come with the switch, it's said that the switch is layer 2 switch..