Spanning vlans across access switches in distribution block.... please help

Hi All
Can someone please explain why Cisco states that in a Campus Hierarchical modle if Vlans are spanned across Access switches in a distribution block, then the Distrubution to distribution link should be Layer 2. Is this really necesary or just a recommendation, and if so why? Can't this link be a L3 link when spanning vlans across Access switches in distribution block, as I understand the benefit of having a L3 distribution to distribution link so that SPT is avoided.
Please help

Hello,
The cisco recommended design is L3 links, but these is only possible if you have no vlans you need to span over the hole network.
It depends on your topology or what you want achieve.
If you need for one or more vlan's spanned the LAN, you need to use a layer 2 connection between all switches and between distribution too.
In my company we have for example a few vlans for restricted areas, like device management or else, so we can't use L3 Links in the distribution area because these vlan's are terminated at the firewall. I think these is good thing.
I would recommend you if you don't have to span one or more vlan's across the network to use L3 Links, specially in the case of redundancy way's. So you need no spanning-tree, but need to use other protocols like GLBP or else. The works faster and are not so confusing (for some people) as STP.
best regards,
Sebastian

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