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Policy Routing - Unix and MS (Dare I ask?)


Need to route out of a dual homed Unix and Windows box based on the source address or source interface as not to follow the default route.

ie, Packet arrives at host x on interface eth0 but the default route is out of eth1 so I get assemetric packet forwarding on the box.

I think ipfw is the way to policy route on unix, but anyone got a plan for windows?

Many thx indeed, and kind regards,


  • Other Network Infrastructure Subjects

Re: Policy Routing - Unix and MS (Dare I ask?)

The standard action, as performed by router software (such as Cisco IOS), is to select the next hop address and the output device. I will refer to this action as a "match & set" style of action. However, Linux takes a much more flexible approach. In Linux, there are several actions to choose from. The default action performs a route lookup from a specified destination-based routing table. The match & set action then becomes the simplest case of Linux route selection, which is realized when the specified destination-based routing table contains only a single default route. Linux supports multiple routing tables, containing multiple standard destination routes. Bear in mind that each of these routing tables is the same as the entire routing table for any other OS. Linux effectively provides 255 Ciscos to choose from. (For number freaks, Linux 2.2.12 supports 255 routing tables, 255 aggregate realms, and 232 (4294967296 decimal) policy rule priorities.

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