Filter-based publish/subscribe and content-based routing have been proposed for flexible information dissemination in distributed environments. A content-based router is part of an overlay structure, in which each router forwards events to neighbouring routers and local clients based on their interests. Filter merging or summarization has been proposed as an optimization strategy in this environment. These techniques combine filters to reduce the number of propagated filters and thus the size of distributed state. In this paper, we present the algorithms for generic dynamic filter merging and discuss integration with routing tables. The algorithms are based on a formal framework of merging rules. Experimental results are examined and analyzed for both desktop systems and small devices. The results indicate that dynamic filter merging is feasible given that the workload is mergeable.