Automatic source routing

Emmanuel Thierry ml at
Wed Sep 25 15:08:06 CEST 2013

Le 25 sept. 2013 à 13:28, Phil Mayers a écrit :

> On 25/09/13 11:48, Sander Steffann wrote:
>> Hi,
>>> My reading of his original email was that he was *sending* pings,
>>> not receiving them. Perhaps I was mistaken.
>> Sorry, you are correct. He wrote:
>>> Unfortunately, when performing, for instance, a ping from one
>>> specific interface or source address, the ping always use the most
>>> recent default router.
>> He is however sending from a specific source address, so it is still
>> not related to source address selection ;-)
> Doh! Of course...

As a summary:

1/ In the case "-I <slaac_eth2>"
The source address is constrained (bind to address <slaac_eth2>). The packet goes out by eth1 but with the right source address <slaac_eth2>, only the routing is concerned.

2/ In the case "-I eth2"
The source address is not constrained, only the device (setsockopt IPV6_PKTINFO <ifindex_eth2>). The packet goes out by eth1 with the source address <slaac_eth1>, the source address selection is concerned.

3/ In the case "-I <slaac_eth2>%eth2"
The source address and the device are constrained (bind to address <slaac_eth2> with scope id <ifindex_eth2>). The packet is correctly routed unless the routing cache already has an entry for this destination.

Best regards.
Emmanuel Thierry

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