Research into large-scale distributed systems often relies on the use of simulation frameworks in order to bypass the disadvantages of performing experiments on real testbeds. SimGrid is such a framework, that is widely used and mature. However, we have identified a scalability problem in SimGrid’s network simulation layer that limits the number of hosts one can incorporate in a simulation. For modeling large-scale systems such as grids this is unfortunate, as the simulation of systems with tens of thousands of hosts is required. This paper describes how we have overcome this limitation through more efficient storage methods for network topology and routing information. It also describes our use of dynamic routing calculations as an alternative to the current SimGrid method which relies on a static routing table. This reduces the memory footprint of the network simulation layer significantly, at the cost of a modest increase in the runtime of the simulation. We evaluate the effect...