On 2013/03/13 14:02, Fleuriot Damien wrote: > > On Mar 13, 2013, at 1:52 PM, Schrodinger <schrodin...@konundrum.org> wrote: > > > On 2013/03/13 12:27, Mark Martinec wrote: > > > > Hi Mark, > > > >> On Wednesday March 13 2013 10:17:27 Schrodinger wrote: > >>> ifconfig_re0_ipv6="inet6 2001:41D0:2:E7c4::1 prefixlen 64" > >>> [...] > >>> Voodoo, indeed... I'm sure there's a /48 used somewhere but to be more > >>> specific, or rather obvious, my default gateway resides at the boundary > >>> of a /56 - 2001:41D0:2:E700::/56 > >> > >> Having multiple IPv6 subnets on the same wire is asking for trouble. > >> > > > > This isn't my network so I don't have any input into the matter. This > > is the OVH configuration for their dedicated servers, at least in my > > product range. > > > >> For example, I believe an ICMP redirect still (in 9.1) does not create > >> a temporary route: > >> http://www.freebsd.org/cgi/query-pr.cgi?pr=152791 > >> which beat us hard time (random unreachability between hosts), > >> having to rearrange that legacy segment which happened to have > >> two subnets on the same wire. > >> > >> The static routes destinations must be directly reachable (on-link). > >> > > > > Does adding the interface route not put the default gateway on-link > > though ? > > > >> Either use a single /56 for the whole LAN, adjusting the prefix > >> length on each interface, or provide a router within each subnet. > >> > > > > If I am to change my prefix length to /56 this means that anyone else in > > that /56 who is configured with a prefix length of 64 will be routing to > > me and I will be swicthing to them.... This could cause problems. > > > I fail to see how they would be routing to you and you would be switching to > them. > > > OVH allocates a /64 per customer. > To avoid having to setup 1 gateway per customer, they set up a single one > within a /56 , allowing for 256 /64s > This mimics the situation where your host gives you a /32 ipv4 withing a /24 > network and uses a single gateway, again for 250ish customers. > > Whenever an IPv6 packet arrives on OVH's router for your /64, it is routed to > your server. > I don't see how this qualifies as "another customer routing to you" ? >
I am informed that I must configure my interface to /64 by OVH. The same as everyone else. So if everyone was on a /64 then we will send packets to each other via our shared default gateway. E.g.: I am 2001:41d0:2:e7c4::1/64 My default gateway is 2001:41d0:2:e7ff:ff:ff:ff:ff If I wanted to communicate with a host in 2001:41d0:2:e7c5::/64 and his default gateway is also 2001:41d0:2:e7ff:ff:ff:ff:ff then we will route packets to each other. Correct? If I were to change my interface prefix length to /56 my host would no longer consider the need to send packets to the default gateway for any host within this /56. I would simply perform Neighbour Solicitation on my link. E.g.: I am 2001:41d0:2:e7c4::1/56 My default gateway is 2001:41d0:2:e7ff:ff:ff:ff:ff If I wanted to communicate with a host in 2001:41d0:2:e7c5::/64 and his default gateway is also 2001:41d0:2:e7ff:ff:ff:ff:ff then I would switch to him because the /56 is "on-link" to me but to the recipient he must route to me via his default gateway. Correct? C. -- +---------------------------------------------------------------+ Quidquid latine dictum sit, altum sonatur. MSN: sch...@hotmail.com ICQ: 112562229 GPG: http://www.konundrum.org/schro.asc
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