Transparent network service migration across service devices

A controller system comprising:

• one or more processors;
• one or more networking interfaces configured to transmit and receive data;
• and
• a non-transitory machine readable medium storing a program for execution by the processing units, the program for migrating a network service at a first device to a second device without interrupting traffic flows for which the network service is being performed, the network service associated with a particular Internet Protocol (IP) address, the program comprising sets of instructions for:
• instructing the first device to migrate the network service to the second device, wherein the migration includes sending, to the second device, state information associated with at least one existing flow currently serviced by the network service at the first device;
• and
• instructing the second device to send a gratuitous address resolution protocol (GARP) message to an upstream network device to associate the particular IP address with a particular network interface of the second device at the upstream network device such that future traffic destined for the particular IP address received at the upstream network device is directed to the particular network interface of the second device,
• wherein, after the GARP message is sent by the second device but before the state information for a particular existing flow is sent to the second device, the second device (i) receives a packet belonging to the particular existing flow and (ii) forwards the packet to the first device for processing.

A non-transitory machine readable medium storing a program for execution by a set of processing units, the program for migrating a network service at a first device to a second device without interrupting traffic flows for which the network service is being performed, the network service associated with a particular Internet Protocol (IP) address, the program comprising sets of instructions for:

• instructing the first device to migrate the network service to the second device, wherein the migration includes sending, to the second device, state information associated with at least one existing flow currently serviced by the network service at the first device;
• and
• instructing the second device to send a gratuitous address resolution protocol (GARP) message to an upstream network device to associate the particular IP address with a particular network interface of the second device at the upstream network device such that future traffic destined for the particular IP address received at the upstream network device is directed to the particular network interface of the second device,
• wherein, after the GARP message is sent by the second device but before the state information for a particular existing flow is sent to the second device, the second device (i) receives a packet belonging to the particular existing flow and (ii) forwards the packet to the first device for processing.