Hybrid Topologies

Hybridization of multiple topologies is useful in larger, more complex networks. It allows the WAN to be tailored to actual traffic patterns instead of trying to force-fit those patterns into a rigid topological model. In other words, the basic topologies presented in this section are examples of constructs intended to stimulate your creative thought. There are no limits on the topological variety that can be introduced to a WAN. The effectiveness of each topology, and subsequent combination of WAN technologies, depends directly on your particular situation and performance requirements.

Multitiered networks, in particular, lend themselves to hybridization. As previously discussed, multitiered WANs can be hybridized by fully or partially meshing the backbone tier of routers. Although there is no right or wrong way to build a hybrid topology, one example of this WAN is illustrated in Figure 13-8.

Figure 13-8: A hybrid topology.

Figure 13-8: A hybrid topology.

Hernial i'-;ulef Hojki Houtei

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Usei Lonaumr L1 User Locality E Ust- .ocali^i F User Locality ü

An effective hybrid topology may be developed in a multitiered WAN by using a fully meshed topology for the backbone nodes only. This affords fault tolerance to the network's backbone and can provide some of the hop-minimization of a full mesh network without experiencing all its costs or incurring its limitations on scalability.

Building Internetworks

Fully meshing the backbone of a multitiered WAN is just one form of hybridized topology. Other hybrids can also be highly effective. The key is to look for topologies, and subtopologies, that can be used in combination to satisfy your particular networking requirements.

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