Cisco Technology, Inc.

Douglas McLaggan

Ian Herbert Wilson

Mark Denny

Suresh Satapati

Rick L Williams

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 are partitioned into address blocks, one of which is assigned to a gateway device. Using the unique IP addresses in its assigned address block, the gateway device translates local IP addresses of hosts 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, that virtual MAC address is re-assigned to an operating gateway device in the redundancy group to permit continued forwarding of the host's packets destined for outside networks.

Network address translation with gateway load distribution

The distribution of traffic flows in a load-sharing redundancy group that includes a first gateway device and a second gateway device includes assigning a first set of forwarding addresses to the first gateway device and a second set of forwarding addresses to the second gateway device. The redundancy group distributes forwarding addresses to hosts which in turn use the distributed forwarding addresses to send packets to the redundancy group. The traffic flow for each of the assigned forwarding addresses is measured and may be compared to a target traffic flow. The traffic flow is adjusted to close in on the target traffic flow. Adjustment of the traffic flow can be accomplished either by changing the existing measured traffic flow by re-assigning a forwarding address originally assigned to one gateway device to a different gateway device or by altering future distribution of forwarding addresses so that additional traffic is sent to one or more forwarding addresses having lower measured traffic. The gateway devices can be routers using virtual Media Access Control (MAC) addresses as forwarding addresses. The redundancy group may also be configured to provide failover services in the event that one of the gateway devices ceases operation.

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Edinburgh, United Kingdom

Douglas McLaggan