On 2015-10-02, Martin Pieuchot <m...@openbsd.org> wrote: > On 01/10/15(Thu) 19:00, Daniel Gillen wrote: >> # ndp -p >> 2001:XX:XX:7c5::/64 if=pppoe0 >> flags=LAD vltime=2592000, pltime=604800, expire=29d23h59m47s, ref=2 >> advertised by >> fe80::46d3:caff:fe9c:ef00%pppoe0 (no neighbor state) >> 2001:XX:XX:707::/64 if=pppoe0 >> flags=LAD vltime=2592000, pltime=604800, expire=29d23h58m45s, ref=2 >> advertised by >> fe80::46d3:caff:fe9c:ef00%pppoe0 (no neighbor state)
The lifetimes that your ISP are sending (2592000 seconds = 30 days) seem rather long especially if they're not static. Though one of my ISPs are using the same (they also happen to be rtadvd defaults). My other ISP are doing vltime 18000 pltime 1800 which seems more reasonable. (chlim=64, O router_ltime=1200, reachable_time=0, retrans_time=0)(mtu: mtu=1500)(prefix info: LA valid_ltime=18000, preferred_ltime=1800, prefix=2a02:xxxx:xxxx:3::/64) > I can confirm that our kernel does not remove prefixes if a router stops > to advertise it. That is correct. RFC4862 says " It is up to system administrators to set appropriate prefix lifetimes in order to minimize the impact of failed communication when renumbering takes place. " > Although it's unclear to me *when* we should remove > this prefix (and the associated autoconf address) except when it expires. As far as lifetimes are concerned, it seems like we are already doing the right thing. I think it would probably make sense to remove an autoconfigured prefix/address if an interface goes down (and one could argue for this being the right thing to do for IPv4/DHCP as well - I lost count of the number of times I have to manually remove addresses so I can continue to reach my home subnet after I've unplugged the laptop).
