Help about LAN architectures

[Yea9632]

Hey everyone !

Sorry if i'm in the wrong section

i'm looking for some documents or any advice that can help me to understand how LAN networks can be built ( Core - Distribution - Access ) and especially how can i choose switches and justify these choices ( especially that many companies now use nexus switches , which were, as i know,  dedicated for Datacenter environments )

sorry for my bad English !    

[Mark Malone]

Yes Nexus are for DC usually , 6500s core switches , 4500 distribution , 3800s or 2900s as access but it can depend as well on your network requirements and the throughput required and what features are needed for each layer smaller networks may have only 45s as core and 38s as distribution  , this doc below explains the different designs , regarding switches theres a lot of choice out there what i provided are just standard models you would see in those types of setups

http://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Campus/Borderless_Campus_Network_1-0/Borderless_Campus_1-0_Design_Guide/BN_Campus_Models.html#wp1237946

http://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Campus/HA_campus_DG/hacampusdg.html#wp1107687

HTH

[Yea9632]

Thank you for your helpful answer

so , after reading this, choosing 65s as core switches or nexus 7K for example,  is depending firstly on the size of the company and secondly on futures that the switch chosen can provides for example ( FabricPath, Virtual portchannel ... )

i think , to choose the right switch, i have to compare features too, to see which one is decent for the company

my problem is i can't find features like those i mentioned before, in Cisco Catalyst 6500-E Series Chassis Data Sheet as an example, maybe it's supported, but where is mentioned  ?! 

is VSS =  portchannel ?

[Mark Malone · Accepted solution]

Hi VSS is basically a couple of 6500s tied together by links usually 20-40gb and they act logically as 1 unit for full redundancy and power , so you get all the modules, power supplies and hardware working together but when you log in to its ios its just one running configuration

Our core where all our SVIs route out of is a VSS core there a solid setup

http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-6500-virtual-switching-system-1440/prod_qas0900aecd806ed74b.html

Features like vpc , fex etc only exist in Nexus there a completely different architecture and ios(nx-os) but similar enough if you know ios its easy enough to pick up the basics most of the same commands work or are just slightly different syntax you can tab out

If you want to see what features are available for models use this link for Cisco feature navigator

http://tools.cisco.com/ITDIT/CFN/jsp/index.jsp

[Yea9632]

Thank you sir for your help 

[Leo Laohoo]

This will depend entirely on the core-distro-access switch models you're going to be using.  Look at Nexus family of switches and look at Instant Access switches (6807X/6880X & 6800IA).  The physical separation of the core-distro-access switches are now a logical separation.  Nexus 7K have several copper line cards.  This enables admin to hook their servers straight to the core.  

Gets even weird with IA or Nexus 2K.  The IA and/or Nexus 2K switches maybe physically separate but all the configuration is done on the parent switch.  

[Yea9632]

You mean that, physically , we can use nexus 7K series switch, but logically it will provide the Core/distribution and Acces layers all together but with a logical separation ?

[Leo Laohoo]

You mean that, physically , we can use nexus 7K series switch, but logically it will provide the Core/distribution and Acces layers all together but with a logical separation ?

Yes, correct.  

You can potentially hook Nexus 2K straight to the Nexus 7K.  This means all your configuration will be on your Nexus 7K.  So this means the Nexus 7K could be all three in one physical box but functional as three layers.

[Yea9632]

But how can i provide, the access layer, by using the nexus 7000 only ?

for example i need 10 switches from 2000 catalyst series just to provide access , imagine the number of ports , how can any chassis-switch ( even the biggest one ) provide all the 3 layers, if the access layer only, have too many ports

i guess that we can have distribution + core layers in the nexus 7K, and we need also, and certainly catalyst 2K switches

if you meant that logically we can use the nexus 7K to manage all the 3 layers and physically we'll have 3 layers or 2 as minimum number of layers, it's OK i got it ( centralizing the management )  

but using a single chassis logically as physically to provide the 3 layers at the same time, i just didn't understood it.

[Leo Laohoo]

But how can i provide, the access layer, by using the nexus 7000 only ?

With Nexus 7K, you can plug the servers directly into the 7K chassis.  So that makes the 7K an "access layer" switch.  

The Nexus 7K can also be a distro for 6K/5K as well as 2K.  So this means it's a distro layer switch.

but using a single chassis logically as physically to provide the 3 layers at the same time, i just didn't understood it. 

This is a theoretical discussion, ain't it?  

[Yea9632]

With Nexus 7K, you can plug the servers directly into the 7K chassis. So that makes the 7K an "access layer" switch

for me, access layer allow  my end users to be connected too , where can i do it in that case ? 

sorry if i misunderstood something, i'm just trying to understand different possibilities 

thank you

[Joseph W. Doherty]

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Posting

Core/distribution/access is just a way to label a 3 layer hierarchy, which, especially with current equipment, can scale rather large.  If you don't need 3 layers for your size network, two is just fine too, those are often call collapsed cores.  Sometimes you don't even need two layers, as just one or two devices can host all your devices.  (For the latter, consider how many ports 6800s with IAs or Nexus with FEXs can host.)

When you have multiple layers, you don't have to have the same L2/L3 capabilities on all layers.  Traditionally, the edge or access layer was the most "dumb", offering just simple L2.  Today, you might have L3 at the edge.

The distro/core layers could be of different combinations of L2 and L3 features, for example, distro might be L2 while the core was L3, or the inverse (L3 distro and L2 core), or both L2 or both L3.  Which to use was often a difficult decision; cost often a major determinant.

[Yea9632]

From that, understand that we have not to respect obligatory  an exact model, it depends  on what we need (features and end-users number)