Network address translation with gateway load distribution

Abstract

Gateway and NAT services to a single host or large number of hosts on a local network using a redundancy group having gateway devices. A pool of unique IP addresses (310) are partitioned into address blocks (310a-310d), one of which is assigned to a gateway device (212, 214, 216, 218). Using the unique IP addresses in its assigned address block, the gateway device translates local IP addresses ofhosts on a local network to unique IP addresses from the gateway device's assigned address block for host packets destined for outside networks and creates a mapping of the translation. The gateway device notifies other gateway devices in the redundancy group of the mapping. A master mapping database or a local mapping database is updated whenever one of the gateway devices performs a translation. In the event that one of the gateway devices ceases forwarding of outgoing packets for a host using the gateway device's virtual MAC address (VMAC), that virtual MAC address is re-assigned to an operating gateway device in the redundancy group (212, 214, 216, 218) to permit continued forwarding of the host's packets destined for outside networks.

Description

technical field [0001] The present invention generally relates to network systems using redundant or standby devices that work together in redundancy groups and load sharing arrangements to provide virtual router services. More specifically, the present invention relates to methods and apparatus for providing network address translation services while allowing packets to be forwarded using a load-distributing virtual router. Background technique [0002] Private and / or local networks are typically connected to the Internet through one or more gateway devices (eg, routers) to enable hosts (PCs or other arbitrary network entities) on the local network to communicate with nodes on the Internet. Typically, a host sends packets to locations identified using addresses (eg, Internet Protocol or "IP" addresses), both within its local network and on the Internet. In order to receive packets from the Internet, the local network or a host on the network must have a globally unique add...

AI Technical Summary

Problems solved by technology

[0020] However, if the failed gateway device is also using NAT to provide translation services to the host, then the translation database or other information is lost, or the AVF to which the failed AVF's vMAC address has been assigned cannot be accessed

Thus, due to the structure and operation of load sharing schemes such as Cisco's GLBP system, NAT (translation) services have not been provided at the same time

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