Split Horizon with Poison Reverse Setting Causes Incorrect RIP Updates on Multiple Adapters (240059)

SYMPTOMS

When you configure Routing Information Protocol (RIP) with multiple adapters and with all the default settings (including the Split Horizon with Poison Reverse advanced settings), the RIP updates that are sent out have the correct metrics for both of the RIP routes. However, RIP also advertises the routes that it learns on the same subnet with a metric of 16 (poison reverse). On the Routing and Remote Access Services (RRAS) computer that receives the RIP updates (with the poison reverse update), the route should not be processed because RIP already has a better route for that subnet (subnet A). It should also distinguish the fact that this update is from a computer that is not the destination router for that route to subnet A. However, RRAS processes that route and therefore discards out a good route in favor of an unreachable route (metric = 16). Any computer on its own remote subnet cannot reach this subnet (subnet A), which now has a metric of 16.