STP and InterVLAN routing topology question

StonedHitman

What I did here was setup pvst and threw in intervlan routing to route between the two vlans 1 and 5. Everything pings and works as it should but I have a question, Is switch 2 at the top right a good spot to connect my router? I wasn't sure which switch I should connect the router or if it even mattered(I just chose it cause it was a root bridge). What concerns me though is, if for whatever reason switch 2 were to go down, I'd lose my routing between vlan 1 and 5. This is a new task for me cause I never combined STP with a router on a stick setup so any insight is appreciated.

gorebrush

Well - have a think about it.. The STP only affects the loops that are built between the four switches right? As long as traffic can traverse all switches for all VLAN's, despite having a link down - will it matter?

Instead of me blindly telling you the answer - what would happen if S2 decided to block the link between itself and S4? All depends on your STP topology. What one is the root bridge for each VLAN?

StonedHitman

gorebrush wrote: »

Well - have a think about it.. The STP only affects the loops that are built between the four switches right? As long as traffic can traverse all switches for all VLAN's, despite having a link down - will it matter?

Instead of me blindly telling you the answer - what would happen if S2 decided to block the link between itself and S4? All depends on your STP topology. What one is the root bridge for each VLAN?

I'm not talking about if a single link on S2 was down, but the entire switch. I would lose my routing between vlans. But pc's on vlan 1 can still communicate and pc's on vlan 5 can still communicate. I was just wondering how others might configure router on a stick while also using spanning tree(specifically pvst+) and what switch they would use to connect to the router.

Jon_Cisco

It seems to me that with router on a stick you are already accepting a single point of failure.

I don't have any experience with it but I wonder if they would build that much redundancy into a router on a stick configuration. Good question sorry I don't have a better answer.