Soon to invest in datacenter LAN switches..

Unanswered Question
Jun 26th, 2008

..and need some advice to choose the most appropiate LAN switches. Unfortunately my knowledge of cisco switches is limited :/


What we want to accomplish is to install 1 24-port/48-port switch in every server rack, connect all servers in the rack to this switch, trunk 2-4 ports which are then connected to a central router (7609). However, im not really sure if a layer 3 switch is necessary? Why would i want to choose a layer 3 model such as for example the 3560G and not a simpler model such as the 2960G. What features of the 35xx series switch would be useful in a datacenter environment to prefer that switch over some 29xx model? One of the main reasons for investment is to reduce the amount of TP cables.


Thankful for any help!


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Joseph W. Doherty Thu, 06/26/2008 - 09:57

If you're not going to take advantage of edge routing, you're correct, a L3 switch used as a L2 switch isn't going to offer much more than a true L2 switch. However, the stackable 3750 L3 switches, offers an interesting variation even when used only as L2 devices.


If the server row is serviced by multiple stack members, you might need less devices within the row since servers can be patched into any stack member. The stack is managed as one device. If working with fiber uplinks, 10 gig starts to become attractive when compared to similar bandwidth provided by multiple gig fiber, when you consider the price of connectors.

tomek0001 Thu, 06/26/2008 - 10:34

When trying to decide which switch to pick you should look at the traffic demand on your network. How much bandwidth will the switch need to switch. Different models have specification, for example the 2960 has a backplane bandwidth of 16 Gbps or 32Gbps based on the model and 3560 has 32 Gbps. These models also have different rates of how many packets they can switch:


• Catalyst 2960PD-8TT-L: 2.7 Mpps which means it can only switch 2.7 mega packets per second


compared to 38.7 Mpps (Cisco Catalyst 3560G-48TS, Catalyst 3560G-48PS, Catalyst 3560G-24TS, and Catalyst 3560G-24PS);


All of these stats you can find in the performance section at http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps6406/product_data_sheet0900aecd80322c0c.html


and http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps5528/product_data_sheet09186a00801f3d7d.html


(please rate if you found this helpful)

glen.grant Tue, 09/01/2009 - 03:28

You can always look at the 2975 series which is a layer 2 stackable switch with POE if needed.This has a 32gbps stackring like the 3750's. To see port utilization on a 2960 or 2975 you can do a "show controllers utilization" command. Wish all cisco switches supported that command.Only available on the lower end switches , go figure!!!For other switches probably the "show int summary" command is the easiest way to look at throuput on the ports.

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