Router and Method for Operating a Communication System Having Redundant Routers

A method for operating a communication system having redundant routers, the method comprising:

• forwarding, by routers, datagrams within the communication system from source communication devices to destination communication devices based on routing information stored in routing tables of the routers;
• configuring a virtual router having an assigned group of a plurality of routers and an allocated virtual data link layer address as a respective default gateway for communication terminals;
• selecting, by routers from the same group assigned to a virtual router among one another, one router which is operated as an active default gateway, the routers which are not operated as active default gateway being configured and operated as reserve gateways;
• adopting, by the reserve gateways, respective address allocations transmitted by a respective active default gateway in their configuration directly and without results from an independent training procedure for address allocations;
• selecting, by the reserve gateways, a new active default gateway among one another in an event of failure of a previously active default gateway;
• adopting, by the new active default gateway, the address allocations transmitted before the failure and allocating the virtual data link layer address to the virtual router as the active default gateway for its operation;
• requesting, by the reserve gateways, a transmission of stored address allocations between data link layer addresses and network layer addresses of detected communication devices from the respective active default gateway;
• and
• transmitting, by the respective active default gateway, all stored address allocations in bundled form to a requesting reserve gateway in each case only upon a request for stored address allocations which is received from a reserve gateway;
• wherein a quality of a synchronization is testable by the reserve gateways at any time by virtue of the reserve gateways specifying a number of received address allocations in their respective request.

A router comprising:

• a plurality of connections for connection to one communication device in each particular case;
• a processor;
• and
• a memory device for storing routing information in routing tables;
• wherein the processor, when executing, causes the router to:
• forward datagrams from source communication devices to destination communication devices based on routing information;
• select from a group of a plurality of routers which is assigned to a virtual router, together with these routers, a router operated as an active default gateway, the virtual router having an allocated virtual data link layer address and the routers which are not operated as active default gateway being configured and operated as reserve gateways;
• adopt, as a reserve gateway, each address allocations transmitted by the respective active default gateway in its configuration directly and without results from an independent training procedure for address allocations;
• select, together with other reserve gateways, a new active default gateway in the event of failure of a previously active default gateway;
• and
• adopt, as new active default gateway, the address allocations transmitted before the failure and the virtual data link layer address allocated to the virtual router as active default gateway for its operation;
• and
• wherein the processor, when executing, further causes the router to:
• request, as the reserve gateway, from the respective active default gateway, a transmission of stored address allocations between data link layer addresses and network layer addresses of detected communication devices;
• transmit, as the active default gateway, all stored address allocations in bundled form to a requesting reserve gateway in each case only upon a request for stored address allocations which is received from a reserve gateway;
• and
• test, as reserve gateways, a quality of a synchronization by virtue of the router specifying a number of received address allocations in its respective request.