I need help in choosing the right switch

Unanswered Question
Sep 17th, 2007

Hi guys,

I need help in choosing the right switch a 6509 or 4500 LAN switch that can support 250+ employess at each office with Fiber blades and Ether RJ45 blades. We are currently on Extreme switch and need to move away. I need help in choosing the right siwtch an dthen get a price through our reseller.

can someone please let me know of th echoice sthat we have. we have 6 VLANS using fiber links from the Core extreme switch to floor closets terminating at the closets on Cisco 3550 CAT swicthes.

I need to move to Cisco on the Core to use it as Core and Dist swicth.

Pls advise.


I have this problem too.
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m-abooali Mon, 09/17/2007 - 11:30

hey Thanks. one question? what does passive backplane means here?

i wasn't able to extract the backplane speed reading that specifications?

Please advie.



Paolo Bevilacqua Mon, 09/17/2007 - 11:38

Actually the 3750 switches will be fine as well. Fast, modular, economic, I like these switches very much. The newer -e version support 10Ge as well.

m-abooali Mon, 09/17/2007 - 11:50

How these switches can be used for the core and distribution? what is the backplane speed? does it support Fiber blades?



Paolo Bevilacqua Mon, 09/17/2007 - 13:15

All the info is in marketing section. The non-E backplane has 32 Gbps, the E, much more. Some model come with SFP ports where put the fiber of your liking.

The switches can be used for everything.

Joseph W. Doherty Mon, 09/17/2007 - 17:51

For new deployments, choosing between the 4500 and 6500, I would recommend the 6500. One issue I see with the 4500 is the limitation of 6 GB per slot as desktop gig and 10 gig uplinks becomes more common.

Like Paolo, I too very much like the 3750 and 3750-E series, but usually recommend them for just L2 access edge devices in larger deployments. Their features aren't as rich as 6500 sups provide, but they can do basic routing very nicely. One issue that was cause for concern with 3750s was a limitation of 32 HSRP groups.

However, for only 250 employees, one stack of 3750, or 3750-Es, could actually probably suffice for access/distribution/core. (You can stack up to 9 units.)

You asked about bandwidth, the 3750, with its 32 gig ring (actually dual 8 GB ring links) compares well against 4500 chassis with it 6 gig fabric or the sup32/sup720 using the 32 gig "classic" bus.

The 3750-E model doubles the bandwidth of the ring links and is smarter about what traffic is placed on the ring and how long it stays on the rings. This model also offers full wire rate to all ports.

You asked about fiber. Both models of the 3750/-Es can use fiber on their uplink ports, usually 2 or 4. The 3750 has a model with 12 SFP ports.

If you are interested in the 3750/-E series, pay careful attention on hardware/software maintenance issue costs and on licensing issues for enhanced image between the two models.

m-abooali Tue, 09/18/2007 - 05:41

Thanks very much for the useful and complete info.

what I really don't understand well is the speed/BW of the backplanes. If I have 5 slots in a 4500 Cisco Switch and each blade say, 48 ports gigi, then what shouold be the backplane spped to accomodate for all of the blades and the gigi ports on the bales?

for this example th eback plane must atleast support 240 gigi? well, i don't know if this is the case?

is the bus speed different from the backplane speed?

Please advise.


Joseph W. Doherty Tue, 09/18/2007 - 06:29

To answer your question about what bandwidth is necessary to accommodate your line cards depends on whether you want to provide "wire speed". The backplane bandwidth needed is 2x your ports (this assumes you're capable of full duplex) and the pps rate is, for 64 byte packets, 1,488,000 per gig, or about 72 Mpps to support 48 gig ports.

An example of a wire speed Cisco switch/router would be the 4948, i.e.

"Wire-Speed Performance for 10/100/1000 Connectivity

The Cisco Catalyst 4948 delivers wire-speed throughput with low latency for data-intensive applications using a 96 Gbps switching fabric with a 72 Mpps forwarding rate in hardware for Layer 2-4 traffic. Switching performance is guaranteed regardless of the number of route entries or Layer 3 and 4 services enabled. Hardware-based Cisco Express Forwarding routing architecture allows for increased scalability and performance."

For 5 slots of a 4500 to support wire speed would require 5x the performance of the 4948. The 4500 doesn't provide this level of performance. The 6500 with sup720 and 40 gig line cards with DFCs comes close.

Realize in the real world we rarely have an environment that's going to drive ALL ports at line rate at the same time. So you can chose hardware that provides necessary performance for the expected load.

"is the bus speed different from the backplane speed?"

Could be the same or could be different. "Bus speed" would normally imply a bus architecture (like a shared hub) for interconnecting line cards. "Backplane speed" might refer to the bandwidth from the chassis to the card or might refer to the total bandwidth of a the chassis fabric. For instance, the fabric on a sup720 provides 720 Gbps and either one or two 20 gig connections to the line cards. (It also supports one or two 8 gig connections to line cards and a shared 32 gig bus.)


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