Performance 3560 as DISTRIBUTION Switch

Unanswered Question
May 7th, 2007

Can a Catalyst 3560G-48PS switch perform well as a distribution switch for a LAN of about 350 users, for intervlan routing between two VLANs, where VLAN1 has 250 users and VLAN2 has 100 users? Would this function overuse the switch capabilities? Would it be a better option to add this switch for wiring closset and perform inter vlan routing throuhg the gateway a router Cisco 2821? I know this would latency to the inter vlan routing function.

I have this problem too.
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Amit Singh Mon, 05/07/2007 - 10:13


This should wofrk without any problem. As you are using 3560 as distribution switch so to uplink Vlan 1 users you need atleast five 48 port layer 2 switches and for 100 users you need atleast 2 48 port switches. Which means that your total uplinks from access switches to the distribution switch would be 7 Gbps link. This will work for you as 3560's have 32Gbps switching fabric and should not give any performance issues in the design.


-amit singh

ciscomv79 Mon, 05/07/2007 - 10:31

Hi thanks for your answer. There is something I forgot to mention. My 7 switches are connected in a bus topology (not in a star since my 3560 only has 2 active SFPs), on a fiber backbone, where 3560 is on one extreme of the bus. Will this create a bottleneck or reduce performance ? In such case I would rather use de router. Is there any Cisco documentation where I can demonstrate this switch will work ok in L3 for this environment ?

Thanks in advance.

Amit Singh Mon, 05/07/2007 - 10:54


Switch can work in the above reuiqrement but you will eventually come across a lots of issues in the design.This will eventually cross the STP diamater which is recommended as 7 Hops upto which the STP behaviour can be predicted. This will also bring some performance issue in the design if all the switches are pumping an aggregate traffic more than 1Gbps. The same problem will also be seen in the other design where you will use router to do the inter-vlan routing.

My suggestion for you would be to use a 3750-12S switch with 12 SFP ports and have all the switches connect to the 3750 as point-point connection. This will give you a scalable design and best optimal traffic forwarding across the network.


-amit singh

ciscomv79 Mon, 05/07/2007 - 11:44

Hi Amit

Would it be out of mind, to connect all seven L2 switches with UTP CAT 6E (which can provide Gigabit speed) to my 3560, and get rid of the fiber, since I have 48 10/100/1000 ports available on the 3560 and 1 Gibabit port on the rest of the switches?

Amit Singh Tue, 05/08/2007 - 06:53


That would be the best Idea. If possible I would suggest to connect all the access switch to the 3560 using Cat6 in a point-point fashion. That will suffice our need.

-amit singh


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