Route or trunk from distribution layer to access layer

[dan hale]

Hello all, I know this has been covered in the past but, im just looking for opinions.

We will be upgrading two of our campus distribution switches to 6880-x we will have a total of four each in two VSS. The first campus is small and has about 8 IDF's all in the same building. The second is a much larger campus with about three times as many IDFs within multiple buildings.

We are looking into changing our access layer design. Currently we route to our access layer. We are looking to simplify and do one of two scenarios.

1. Create one data subnet and trunk those vlans out to the access layer.

2.Create multiple data subnets, one per closet, and trunk those vlans out to the access layer.

Well use port-chanelling for physical link redundancy.

Part of the reason we are moving away from routing to the access layer is that not all of our switches are stub routing. So there is a level of complexity. It would be nice from our end to supernet these subnets. Not to mention LAN base license will be less cost.

Thoughts?

Thanks,

Dan

[Reza Sharifi]

Hi Dan,

The solution to go from routed access to a layer-2 access should work fine.  It is probably cleaner to use a /24 subnet for each IDF and than a layer-2 trunk (port-channel) to the VSS switches.  This way you can use the minimum license (LAN Base) for all layer-2 switches and have the SVIs on the VSS with advanced licenses.

HTH

[dan hale]

Thanks for the comment. If I have to do a layer 2 approach to the access layer I'm liking this more than one flat data vlan that I span thru out the building.

[Kevin Dorrell]

It seems to bee very much a matter of preference.  Are you using static IPs or DHCP?  The layer 2 approach is better if you have static IPs but you want to be able to move PCs from closet to closet without re-configuring them.  There is the argument that L3 gives you better isolation between the closets in case of any L2 fault conditions like loops.  But honestly, when you only have one uplink on an access switch, are you really likely to get a loop (even if it is actually two links in a port-channel)?

One thing I would say, though, is L3 between your sites.  I would not recommend trying to extend your VLANs between sites.

Kevin Dorrell

Luxembourg