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Campus Switching Design

Nicholas Beard
Level 1
Level 1

Hi folks,

Would like somebody to peer review the following design to put my mind at ease regarding a switching topology.

6 x Cisco 3750 (Stacked)

20 x Cisco 2960 POE

I plan to create a 3 layer hierarchical design (Core, Distribution and Access) making use of 2 3750 switches as the core, the 4 remaining 3750 switches as the distribution, and lastly the 20 2960 Switches as the Access.  This is not a greenfield site therefore currently the customer has the 20 access switches in place and 2 3750 switches stacked.  The customer is intent on stacking the core/dist switches so i have to interconnect all 3750 switches with stacking cables.  This kind of makes the core/dist layers an amalgamation of both.

My plan is to perform the following -

Create two core switches to perform Inter VLAN routing between 5 VLANs -

Management VLAN

Desktop VLAN

Storage VLAN #1

Storage VLAN #2

VOIP VLAN

Two seperate VLANs for Virtualisation without the requirement for routing -

Heartbeat VLAN

Migration VLAN

Create four distribution switches to connect the access switches to.  I don't have the functionality to perform MEC therefore i will etherchannel dual Gigabit connections into the 4 distribution switches (5 access switches at a time).  I realise this is a single point of failure as if 1 distribution switch fails, 5 access switches will be knocked out; but due to the bandwidth requirements of each access switch i have to make use of dual gigabit uplinks via LACP. 

VLANs required on the Access switches will be as follows -

Management VLAN

Desktop VLAN

VOIP VLAN

The gateways for each of the VLANs will be set to the SVI of the two core switches in a manual load balanced method.  I do not plan on using HSRP as this will add an extra level of complexity for administration purposes post completion of project.

Finally, the storage arrays, servers and other devices will all be connected to the distribution layer.  I guess my question would be; would it be more beneficial to perform the inter VLAN routing within the distribution layer or leave it at the core layer?  The breakout to the internet will traverse a firewall directly connected to the core.  The vast majority of traffic will however, be between VLANs within the network.

3 Replies 3

sguirguis
Level 1
Level 1

I would say if the VLANs  overlap multiple distribution switches then routing has to be done at the core.

esomarriba
Level 5
Level 5

Do you have a network design for this?

Jon Marshall
Hall of Fame
Hall of Fame

Nicholas

Is this actually a campus network ie. multiple buildings interlinked or is it simply one building ?

If it is one building you don't really need a core as such, you should look to use your 3750s as collapsed distro/core as you don't really get a major benefit from a core. A core is useful to interconnect multiple sites together.

Not sure what you mean when you say you can't run MEC. The 3750s support MEC so you should spread each access-layer switch across at least 2 of the 3750 stack then you get redundancy.

Not sure why you don't want to use HSRP. If you really want to load-balance then use GLBP which is now supported on the 3750s. Manually setting gateways on clients is actually creating more administration overhead than using either HSRP/GLBP. Both are well understood protocols, especially HSRP, so i don't see how it is creating complexity.

The servers and storage arrays. I would use the 2 3750s you propose to use as the core to connect these up and then connect these switches back to the distro switches. If the vast majority of traffic is inter-vlan then what benefit do you get from a core other than to go to the internet. The internet connection could be connected to the distro switches obviously firewalled.

The above is the way i would approach it based on the info you have given. I'm not saying you cannot use a core but from your description i am struggling to see what benefit it gives ie. firewall access + inter-vlan routing but the inter-vlan routing should be done on the distro switches anyway in the cisco model.

If however you have multiple sites and are using the core to interconnect them then please come back with more details.

Jon

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