The simplest is to indeed use the cost. But be careful that it's not only the cost of the port that is to be taken into account. Just increasing the cost of a port will not necessarily make it blocking. You have to compare in fact the bpdu the port is going to send and the bpdu it receives. Comparing the cost of these bpdus will probably be enough in a simple topology. Even if this document is not directly related to what you are looking for, it explains the port roles: http://www.cisco.com/warp/public/473/146.html#roles
What you are looking for is tuning the port cost so that it becomes alternate.
[toc:faq]The ProblemOn traditional switches whenever we have a trunk
interface we use the VLAN tag to demultiplex the VLANs. The switch needs
to determine which MAC Address table to look in for a forwarding
decision. To do this we require the switch to do...
[toc:faq]Introduction:Netdr is a tool available on a RSP720, Sup720 or
Sup32 that allows one to capture packets on the RP or SP inband. The
netdr command can be used to capture both Tx and Rx packets in the
software switching path. This is not a substitut...
IntroductionOSPF, being a link-state protocol, allows for every router
in the network to know of every link and OSPF speaker in the entire
network. From this picture each router independently runs the Shortest
Path First (SPF) algorithm to determine the b...