hi,
usually with bgp you do the loop prevention with the AS Path. So we use the soo in conjunction with the as-override feature. If you have the as-override feature for some reason in place you can make the prevention with the soo. Sites providing the same prefix information will have the same soo...to identify routes that have originated from a site so that the re-advertisement of that prefix back to the source site can be prevented.
hope that helps you.
Regards
Roger
