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TOPIC: VLAN Routing at Aggregation or Core?

VLAN Routing at Aggregation or Core? 10 years 7 months ago #14535

  • taq
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Would like to know in a standard design a Layer 2 switch is connected to a Layer 3 Aggregation switch and the L3 aggregation switch is connected to a core switch.

If at the layer 2 switch wants to communicate between VLANs, will the VLAN routing be done at aggregation or core switch?

Thanks.
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Re: VLAN Routing at Aggregation or Core? 10 years 7 months ago #14564

  • tHe-SwItCh
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hi

It would be at the L3 switch ! L2 switches by 'emselves can't have Routing between VLANs come what may ....... L3 switches' routing capabilities at Layer 3 are needed for interVLAN routing.
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Re: VLAN Routing at Aggregation or Core? 10 years 7 months ago #14572

  • jwj
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Yes, have your L3 switch do the inter-vlan routing, that way your core will just be used for routing between your various networks. It would be inefficient to extend your VLANs as far as your core. Consider that by having your core doing the inter-vlan routing, it would also inherit the broadcasts that are associated with them. You want your core to be as unencumbered as possible. So basically if you follow Cisco's hierarchical model, you'll see this.

The access layer is for connecting workstations. This is your wiring closet that contains your L2 switches. The L2 switch should connect to the distribution layer, which should be a L3 switch that will have inter-vlan routing, Quality of Service, access control lists, multicasting, etc. Finally, your L3 switches should connect to the core layer, which is the high speed traffic forwarding devices. These can be ATM switches, routers, it could be MPLS, and so on. This layer is just concerned with connecting networks as quickly as possible.
-Jeremy-
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Re: VLAN Routing at Aggregation or Core? 10 years 6 months ago #14668

  • taq
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So, the distribution layer 3 switch can do the inter-vlan routing rather than relaying entirely on the core switch?

Thanks.
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Re: VLAN Routing at Aggregation or Core? 10 years 6 months ago #14675

  • havohej
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yes the distribution device muts route.
, in professiona desings you have 3 herachical layers, acces, distribution and core.

resuming:
access layer gives terminal acces to the wire, entrance point for every pc to the network.

distribution layer responsible por packet handling, sumarization, politics, acls, and routing (routers)

core: forward packets as fast as posible.
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