We propose a data structure-dynamic tree bitmap- for the representation of dynamic IP router tables that must support very high lookup and update rates. In fact, the dynamic tree bitmap is able to support updates at the same rate as lookups and is very competitive with other structures-tree bitmap and BaRT-proposed earlier for dynamic tables. Although the dynamic tree bitmap requires more memory than is required by the tree bitmap and BaRT structures, the required memory remains reasonable. The real value of our structure is its ability to support a very high update rate.