Mikael, > I'm trying to influence my source address selection. First I thought I'd > figure out how it works by default. > > I have a /48. Let's call it 2001:db8:1::/48 > > I created three /64s on the same LAN with A-bit set so clients would do SLAAC > within these: > > 2001:db8:1:0000:/64 > 2001:db8:1:1000:/64 > 2001:db8:1:2000:/64 > > Then I set up loopback addresses on my router: > > 2001:db8:1:0001:1/128 > 2001:db8:1:1001:1/128 > 2001:db8:1:2001:1/128 > > Then I tried pinging each loopback address from a host which has 2 addresses > out of each /64. It now picked a source address within the same /56. I > consistently both on a Ubuntu 13.04 and OSX 10.8.5 machine get the same > behaviour. > > So above means that pinging 2001:db8:1:1fff::1 it would use the :1000: > address, and pinging :2fff::1 would use the :2000::/64 address. > > If I ping outside my /48 it will consistently use the last created address (I > tried adding a 4th lan, 8000, and it then uses that one), which I perfectly > understand. > > When I ping :5000: and so on, it will sometimes use the :0000: address and > not the :8000: that is used for the rest of global traffic. > > I have nothing /56 or /48 magic in routing table or "ip addrlabel list", but > it still seems to be something special when it comes to the same /48 as the > machine has addresses in. > > Any help understanding what is going on is appreciated.
wouldn't this be RFC6724: Rule 8: Use longest matching prefix. If CommonPrefixLen(SA, D) > CommonPrefixLen(SB, D), then prefer SA. Similarly, if CommonPrefixLen(SB, D) > CommonPrefixLen(SA, D), then prefer SB. cheers, Ole
signature.asc
Description: Message signed with OpenPGP using GPGMail
