Need to choose core switch

[himu73]

Hi, I have a network which consists of a data center of 20 servers connected to a switch. Then there is 1000 LAN users who will access this servers as well as internet through a core switch which is connected to router. The server switch is connected to core switch. I want to use Cisco nexus switch for server switch. But, I cannot decide the core switch. Can I use a Cisco Catalyst switch as the core switch. Does it have any disadvantages?

 

[bill001g]

I will assume you have another group of switches that actually connect the 1000 lan cables to. You would have your users packed awful close together if you can get that many cables in the 100 meter limit.

If you have a number of distributed switches running these end users and you run 10g fiber back from them you could just buy another 10g board in the nexus and use it as your core switch also.

If all the cables really do terminate in the same place then you will still need a few larger switches . Even if you could put 1000 cables into one chassis it likely is not a good idea. No matter how redundant they tell you thing are the failures you see in real life always seem to take you down anyway. The devices never seem to just fail they partially fail in ways you can not even guess.

If you mean do you use like 6500 line of catalyst it may not make a lot of difference. It depends on your traffic. It would be important if there was a lot of traffic between the end users machines. In most installation the traffic seems to flow to the server farm and to the internet router.

It does not take much fancy features to run that most any of the layer 3 switch line will do that. The key is to make sure you have enough capacity between the nexus server switch and the other switch. This is why 10 distributed switches with 100 users each connecting with redundant 10g cables would likely perform better that 2 large switches even if you interconnect the nexus and a big catalyst with 40g cables.

 

[himu73]

I will assume you have another group of switches that actually connect the 1000 lan cables to. You would have your users packed awful close together if you can get that many cables in the 100 meter limit.

If you have a number of distributed switches running these end users and you run 10g fiber back from them you could just buy another 10g board in the nexus and use it as your core switch also.

If all the cables really do terminate in the same place then you will still need a few larger switches . Even if you could put 1000 cables into one chassis it likely is not a good idea. No matter how redundant they tell you thing are the failures you see in real life always seem to take you down anyway. The devices never seem to just fail they partially fail in ways you can not even guess.

If you mean do you use like 6500 line of catalyst it may not make a lot of difference. It depends on your traffic. It would be important if there was a lot of traffic between the end users machines. In most installation the traffic seems to flow to the server farm and to the internet router.

It does not take much fancy features to run that most any of the layer 3 switch line will do that. The key is to make sure you have enough capacity between the nexus server switch and the other switch. This is why 10 distributed switches with 100 users each connecting with redundant 10g cables would likely perform better that 2 large switches even if you interconnect the nexus and a big catalyst with 40g cables.

Sorry for the confusion. Actually there will be several distribution switches and access switches to connect the LAN users. These switches will be connected to a core switch. Then, core switch will be connected to router and server switch. When a user want to access a server, he has to travel through the access->distribution(catalyst)->core(catalyst)->server switch(nexus)->server. In case of internet, it will be like access->distribution->core->router->ISP.
I am concerned about the core switch. Does it has to be powerful than server switch?

 

[bill001g]

One of the key advantages of the nexus switches is you have 2 switches and they appear as a single device but are fully redundant.

In your core switch you have to plan a bit more for things like spanning tree for your fail overs.

The key numbers you much watch out for are the total capacity of the cards. Many cards that have 10g interfaces are over committed. They could have 8 ports for a total of 160g of bandwidth but only have 100g between the card and the back plane.

What you need to look for is a device that has enough total backplane speed to run all your users at rate you feel is realistic...not at maximum since that never happens. You then look at the interface card options and be sure you do not put too much data into a single slot.

The core switch will have to have more total backplane than the server switch but it depends how much internet traffic there is. If you are talking even 1g it will have very little effect. How much you need greatly depends on the application. A company that transfers video rendering files all day long will need a much large switch than someone who edit word documents.

Cisco has so many switch lines its hard to choose. Then again if you are buying this equipment new call a cisco partner design of stuff like this is built in to that massive price cisco charges for new equipment.