I'm trying to setup a redudant path within our network from one location to our isp. I'm not very familiar with spanning-tree and i'm wondering if I could get some insight as to what options i need to look into to make sure i have no loop's, storms or stp issues.
I have attached a diagram to show what i want to do. Currently the traffic goes from location 20 to our isp via the green line. I want to use the yellow line if the connection between location 24 and 30 is down.
All links are configured as trunk ports with spanning-tree portfast trunk on.
I'm trunking vlan 800 from location 20 to 24 then to 30. If I trunk vlan 800 from location 24 to 18 to 14 and then to 30 it flap's.
STP should work out the topology for you. However you should not have "spanning-tree portfast trunk" configured on the trunk links.
That command allows the trunk port to being forwarding immediately which is absolutely what you don't want. The command is really designed for servers that are running 802.1q trunks to switches.
So please remove that line from your configurations. When you do add additional vlans to trunk links then be aware they may be a small interruption to that vlans traffic while STP works things out for you.