There could well be an issue there. It is difficult to imagine how the redundancy would work. If the access switch was the only one carrying VLAN 30, and it lost its link to one of the core switches, then both core switches would become HSRP active because they would lose sight of each other. I guess the access switch would just use the active router that it still has a link to. But the other VLANs might be using the other core switch as router, and those would not be able to reach VLAN 20.
All in all, I think a better architecture would be to tie the two core switches together with a good solid trunk carrying all the VLANs. Which is the "normal" architecture.
If you are running a PVST mode (PVST or Rapid-PVST) you can forget about STP. You can probably configure portfast on those ports if they are the only one on their respective vlans. If you are running MST, you're asking for trouble by using access links (I doubt you do so I won't elaborate;-)
As Kevin already mentioned, you might have a L3 issue if say, the uplink between SW1 and core1 goes down. You have to be sure that the interface vlan 20 goes down on core1 so that core1 does not advertise a route to the subnet any more and does not black hole your traffic. I think you are aware of that. There is a feature on Cisco switches that brings down a vlan interface if there is no port forwarding for the vlan on the switch... So you should be ok as long as the only link configured for vlan 20 on core 1 is the downlink to sw1. Because of this requirement, I'm wondering why you want to use switchports. Just configure all your ports as L3 interfaces instead of switchports and you can safely forget about STP.
The feature is called "autostate". This is enabled by default and I don't think there is a CLI to disable it (there might be some engineering commands though). If you have no port forwarding in a given vlan, the vlan interface should be brought down. If you don't see this behavior, this is a bug.
Hi everyone, I would like to thank you in advance for any help you can provide a newcomer like myself!
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