Computer trivia

IP source routing is an option in IPv4 that allows you to specify the route, packets sent by you must follow on their way to destination. Usually the routers decide a best path on the receipt of the packet, but when IP source routing is used, the routers follow the path given by the sender.

However, this feature has been hugely abused for IP spoofing, as a result of which almost all the routers and Operating Systems disable this feature by default. In fact, source routing is completely removed from IPv6.

There will be cases when one wants to source route like the default route being very poor in quality. Also for some academic purposes one might want to enable source routing. So if you are using Windows Vista, here is how IP source routing is enabled (or disabled). By default it is disabled.

Open Windows registry and traverse to

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

Create a new DWORD (32-bit value) here and name it "DisbaleIPSourceRouting" and set its value as one of the following.

“0″ to forward all the packets.

“1″ to stop forwarding source routed packets (default behavior)

“2″ to drop all the source routed packets.

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