Spanning vlans across access switches in distribution block.... please help
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.
Re: Spanning vlans across access switches in distribution block.
If you choose to span your vlans across access switches, then yes, your distribution layer switches will have to have L2 trunks configured between them to pass vlan traffic. The trunk is said to provide "L2 adjacency."
Remember, a vlan is a L2 construct. A device that is part of a particular vlan should be able to conduct L2 communications with another device in the same vlan. So, if you have a host in vlan 10 that hangs off switch 1 and you have another host in the same vlan that hangs off switch 2, switch 1 and switch 2 will have to have a L2 trunk configured between them to allow vlan traffic to pass. OR, if each switch is dual-homed to a distribution layer switch, the L2 uplinks between access layer switches and the distribution layer switch can provide that L2 adjacency.
Moreover, you can have a routed access layer, which typically means that a vlan will be confined to that access switch, HOWEVER< there is a flavor of routed access layer that allows for the placement of a L2 trunk between ACCESS switches to allow the vlan to span across access switches. The uplink to the distribution layer, however, will be a L3 connection.
We are pleased to announce availability of Beta software for 16.6.3.
16.6.3 will be the second rebuild on the 16.6 release train targeted
towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are
looking for early feedback from customers befor...
Introduction Featured Speakers Luis Espejel is the Telecommunications
Manager of IENova, an Oil & Gas company. Currently he works with Cisco
IOS® and Cisco IOS XE platforms, and NX to some extent. He has also
worked as a Senior Engineer with the Routing P...
In this session you can learn more about Layer 3 multicast and the best
practices to identify possible threats and take security measures. It
provides an overview of basic multicast, the best security practices for
use of this technology, and recommendati...