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Sabrina Kilian a écrit :
> Francois Labreque wrote:
>> Sabrina Kilian a écrit :
>>> It is an interesting way to use commodity hardware, instead of custom
>>> stuff. Though, the article does make it hard to take them seriously when
>>> they use lines like "Modern routers are rarely dumb switches anymore."
>> Most comemrcial routers HAVE been switches for the last 20 years. The
>> first packet to come through would be routed by the cpu, but the result
>> of that routing table look up would be sent to an interface cache and
>> all the packets for the same destination after that would be switched
>> directly by the interface hardware, leaving the CPU alone.
>
> Switches have moved up to handling some of the layer 3 protocols and
> doing some of the stuff typically thought of as router work. Managing
> VLANs and the like, and switching stuff between them. If the router
> never had to handle BGP, and the like, then a smart switch could replace
> it. Depending on the switch, it might even work where all you need is
> QoS and some switching between local disparate IP subnet and VLAN.
> However, a smart switch won't replace a router where one is really
> needed; handling all the annoying route finding when you have a more
> complex topology outside the area of your network. At least, I haven't
> seen one that manages BGP. Wiki tells me they may exist.
>
Even if it does appear that the author of the article's experience with
routers is limited to the Linksys or Netgear home stuff, I'm not talking
about "layer-3" switches. I'm talking about a router that does
switching in hardware based on mac-addresses.
> Still, all of this is smart switches moving up to fill the need of
> simpler routers. Any router, barring marketing names, has never just
> switched packets on layer 2 like a dumb switch will.
>
The Cisco 7000 or 7500 series have been doing just that, and the newer
GSR and CRS models do it as well. As I said earlier, the first packet
to come by will be CPU-routed, but all the following ones* for that same
destination will be handled in hardware based on mac-address look-ups.
This is how a Cisco 7000 was able to handle 16M pps with only a 33Mhz
CPU, 20 years ago.
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