The glue (how routing protocol instances interact and exchange routes among themselves) is still little understood or studied.
… refer to the combination of route selection and redistribution procedures simply as the glue logic … the glue logic was introduced as a software enhancement by router vendors (rather than a standard protocol). vendors try to … publishing templates for configuring the glue logic and pointing out common pitfalls … through simple examples.
The routing processes at a router are by default independent: they do not exchange routing information among themselves … route selection allows operators to rank the routes received from multiple routing processes at a router, …: in fact, each routing protocol is assigned a default administrative distance (AD) value.