Access Routers and Core Routers - Placement

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Nov 12th, 2009
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Our office covers six floors, what we're trying to do is build a Wireless LAN.


We are going to have a switch on each floor (6 in total) which will connect to access points. The question being that I've been told I'll need core level switch coming of the router. So Router, Core Switches, Access Level Switch, APs. How many Core switches would be recommended? Would someone be so kind as to explain the principle behind this?


Trying to do as much work as possible to cut costs.


Thanks


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Amit Singh Thu, 11/12/2009 - 11:04
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Hi,


The design for this would go like this :


[WAN router]--> [Core Switches]--> [6 Access switch connected back to core switches with dual uplinks].


In an ideal network design you will have a pair of fiber running from each floor back to core switches located near the WAN routers. You atleast need 2 core switches for redundancy. The core layer of the network has to be highly redundant as it is the heart of the entire network. There are various models available for core layer depending upon the capacity and the traffic requirement.


Even if you have a single pair of fiber from each floor you can atleast use different cores from the fiber and connect it back to the pair of core switches.


HTH


Jon Marshall Thu, 11/12/2009 - 11:05
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Sam


If you are using more than one vlan then you will need something to route between the vlans and this would typically be a L3 switch.


For your setup if you had one vlan per floor for example you could use a pair of 3750 switches as your core devices. These can be stacked and then from each floor switch you could run a L2 cross stack etherchannel to the 3750s for redundancy ie. each floor switch has 2 uplinks - one to each of the 3750 switches so a link failure or a 3750 failure does not isolate the floor.


Note that there are other ways to do this but the above is a common approach. Come back if you have further questions.


Jon

sberman12 Thu, 11/12/2009 - 11:32
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Jon,


Thanks for your reply. Most helpful. Comfirmed some questions i had.


What i would like to ask is, if for example I run the two 3750 switches as my core devices could i then run Catalyst 3560 as my access level switches on each floor to the wireless access points?


Core switches would be connected to the fibre back bone and i'd then interconnect the 3750's with fibre too.


As an example.


Thanks once again.


Sam



Jon Marshall Thu, 11/12/2009 - 11:36
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Sam


You could run 3560 as access-layer switches but you could also look at 2950/2960/2970 switches as well which are L2 only. A lot depends on how many ports you need per floor.


A 3560 is the first L3 capable switch in Cisco portfolio and if you are using L2 from the access-layer then you might not need L3 capable switches. Obviously the L3 switches are more expensive. But yes 3560 switches would work perfectly well.


Jon

Edison Ortiz Thu, 11/12/2009 - 11:38
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i'd then interconnect the 3750's with fibre too.


No. They are stackable switches and the stacking cables will be provided with the switch.


Stacking the switches will provide a higher level of redundancy and faster throughput between 3750s. It also provides single management interface for members of the stack.


Regards


Edison.

sberman12 Thu, 11/12/2009 - 12:14
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My mistake, i was refering to the access level switches. Backbone > 3750 > fiber will connect from the 3750 to the other access switches.


Regards,

Sam

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