Within a communication system having redundant routers, datagrams are forwarded from source communication devices to target communication devices via routers based on routing information stored in routing tables of the routers, wherein for each communication terminal, a virtual router is configured as a default gateway, to which virtual router a group of a plurality of routers is assigned, where routers from the same group assigned to a virtual router select from among themselves a router operated as the active default gateway, the routers not operated as the active default gateway are operated as reserve gateways, and where the active default gateway in question transmits, only upon a request for stored address assignments that is received from a reserve gateway, all stored address assignments to a requesting reserve gateway in bundled form.