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Posted by glen herrmannsfeldt on February 15, 2006, 2:42 pm
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>>> Just what is the difference between a "switch" doing things at the
>>> network layer and a "router" doing things at the network layer?
(snip)
>> I would say a layer 3 switch should have more special purpose
>> hardware, such as would be expected in a layer 2 switch.
>> A router is usually mostly software, with more or less conventional
>> NICs and a COTS processor.
> So, implementation detail is more important than function?
As with the old saying, form follows function. If you can do
it with cheap hardware there is no point in using expensive custom
hardware. As processors get faster, the dividing line will move.
> My understanding is that those big honking "core routers" from the
> likes of Cisco, Juniper, Foundry et al are very much special purpose
> hardware.
Probably. The last time I opened a Cisco router (a lower end
model, about 10 years ago.) I was surprised to see ordinary hardware.
>> I understand that one can run Linux on a Linksys WRT54G, for
>> example.
> It seems that one can run some variant of Linux on just about anything
> with a clock pulse :)
How about the core router mentioned above?
>> Similar to the way a layer 2 switch might have a processor to
>> handle tasks other than packet forwarding, a layer 3 switch might
>> have a similar processing function. Packet forwarding should be
>> done without the involvement of the processor, or with minimal
>> involvement, other than to update routing tables.
> By that definition then the really high-end (and probably not quite so
> really high end) routers from the vendors would be switches.
Maybe. Though the people that buy them probably don't care
what they are called as long as they work up to their
specifications.
-- glen
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