Source-based routing

Source-based routing selects which gateway to direct outgoing client traffic through based on the source IP address in each packet header.

When enabled, source-based routing automatically scans your network configuration to create client traffic rules. If you make modifications to your network configuration, such as changing the IP address of a gateway server, source-based routing adjusts the rules. Source-based routing is applied across the entire cluster and does not support the IPv6 protocol.

In the following example, you enable source-based routing on an Isilon cluster that is connected to SubnetA and SubnetB. Each subnet is configured with a SmartConnect zone and a gateway, also labeled A and B. When a client on SubnetA makes a request to SmartConnect ZoneB, the response originates from ZoneB. This results in a ZoneB address as the source IP in the packet header, and the response is routed through GatewayB. Without source-based routing, the default route is destination-based, so the response is routed through GatewayA.

In another example, a client on SubnetC, which is not connected to the Isilon cluster, makes a request to SmartConnect ZoneA and ZoneB. The response from ZoneA is routed through GatewayA, and the response from ZoneB is routed through GatewayB. In other words, the traffic is split between gateways. Without source-based routing, both responses are routed through the same gateway.

Source-based routing is disabled by default. Enabling or disabling source-based routing goes into effect immediately. Packets in transit continue on their original courses, and subsequent traffic is routed based on the status change. Transactions composed of multiple packets might be disrupted or delayed if the status of source-based routing changes during transmission.

Source-based routing can conflict with static routes. If a routing conflict occurs, source-based routing rules are prioritized over the static route.

You might enable source-based routing if you have a large network with a complex topology. For example, if your network is a multi-tenant environment with several gateways, traffic is more efficiently distributed with source-based routing.