I have a VLAN config question. I was reading this Cisco book about VLANs, VTP, & STP and I saw a configuration I didn't understand. Here it is, There were three switches Main/server switch and two distribution/client switches. Well these swtiches had Vlans 10,11, and 13 on them. Now on the main switch they configured that switch to be the root for VLan 1. On switch two they configured that switch to be the root for vlan 11. On the third switch they configured that one to be the root for Vlan 13. My question is why would you configure a switch to be the root switch of a particular VLAN? What purpose does this serve?
Again this is generally speaking but not not really unless you wanted very specific control over your layer 2 paths.
A common setup is to have a pair of core switches and you make switch1 the root for all odd vlans and the secondary for all even vlans, and switch 2 the root for all even vlans and the secondary for all odds.
If you have a layer 2 access-layer connecting to a pair of distribution switches that do the L3 vlan routing then these would be the switches to set as root and secondary.
Cisco's 3 tier design - core/distro/access is not always that clear cut in terms of physical network infrastructure. Quite often the same pair of switches act as the distro and core.