Stuck in Active
When a router notices a route failure and moves a route from the passive to active state, that router sends Query messages to its neighbors. With a sufficiently large network, particularly when routers exist several router hops away, the number of Queries might not only be large, but there also might be a string of routers that all must wait on multiple Reply messages before they can, in turn, issue a Reply. For example, in Figure 5-13, Router R1 must wait on Routers R11, R12, and R13 to send a Reply. R11 must wait on Routers R21, R22, and R23. R21 must wait on three other routers, and so on—meaning that R1 might have to wait quite a while before getting a response.
Figure 5-13 Network Design That Causes Unreasonably Long Convergence ...
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