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Old 01-30-2012, 12:29 PM   #1
Registered: Nov 2006
Distribution: Ubuntu Hardy
Posts: 69

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Question Reverse Path (packet) Filtering and policy based routing (iproute2)

I have a box with 2 NICs. The default route is via eth0.

The reverse path filtering (feature) of the kernel drops incoming packets where the route to the source IP address of the packet would go out a different NIC than the one it came in.

Policy-based routing ( has helped to alleviate that problem by, in a sense, enabling me to provide a default-route per interface whereby I create a custom routing table and enforce routing rules to use that table.

However, I cannot get this policy-based routing to work the same way for multicast packets, where the source IP address can be pretty much anything. Does policy based routing apply to multicast packets? There are some 'multicast' keywords for the "ip rule" and "ip route" commands but either I am not using them correctly or they have no effect. Has anyone any experience with iproute2 and multicast to avoid dropped packets due to reverse path filtering?


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