> Does anyone have idea about the different between l3 switches and router ?
> if i'm not mistaken, extreme/catalyst has capability to do routing so if l3
> switches can do routing and why i should buy a router for doing routing ?
The word "switch" has no precise meaning today - or to put it another way,
it only means what the marketing people *wants* it to mean.
Having said that, you'll often find that a switch does more of the packet
processing/forwarding in hardware, but sometimes has less functionality
and extensibility than a software based router.
As an example, take the 2948G-L3 which I'm rather familiar with - and
compare it for instance with a 7140 with 2 Fast Ethernet ports.
The 2948G-L3 has 48 10/100 ports and 2 GBIC ports, can forward millions
of packets per second (*much* more than a 7140). Sounds good, doesn't it?
Until you start looking at the limitations, some of which are:
- Fixed configuration, no extensibility. If you want a WAN port, forget
it.
- No ACLs on the 10/100 ports.
- Only IP and IPX.
- Since packet forwarding is done in hardware, the debugging and logging
facilities are not as good as the 7140.
- No possibility of BGP with full routing tables, due to fixed size memory
(too small), but BGP with partial routing tables can be done.
If you have a LAN-only IP-only environment, and the 2948G-L3 fits your
requirements, by all means go for it - it gives very good value for the
price. If your networking requirements are somewhat more complex, you'll
often find that L3 switches alone are not enough.
Steinar Haug, Nethelp consulting, sthaug@nethelp.no
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