a)Five device arranged in mesh topology<- Need huge resource, i.e. each site need to connect to all site, so you need N x N link (physical or virtual), virtual link need high CPU/memory.
Cisco give us some solution to reduce the high CPU/memory one solution is GET.
b)Five device arranged in star topology<- this solution except that if Hub is failed then connect between site is failed, so it recommend that Hub need redundancy by add other Hub.
c)Five device arranged in ring topology<- if one link is failed then all site will not connect to each other
d)Five device arranged in bus topology<- if one link is failed then all site will not connect to each other
