# Unique Routing Path

It is illegal to define a set of routes that permit a message to reach a server by more than one path. TIBCO Enterprise Message Service servers detect illegal duplicate routes and report them as configuration errors.

The following image depicts two sets of routes. On the left, the routes connecting servers A, B, C, D and E form an acyclic graph, with only one route connecting any pair of servers; this configuration is legal (in any zone).

In contrast, the routing configuration on the right is illegal in a multi-hop zone. The graph contains redundant routing paths between servers Q and S (one direct, and one through R and T).

Note: Note that the configuration on the right is illegal only in a multi-hop zone; it is legal in a one-hop zone. For further information, see Zone.
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