In the case you list below, host1 and host2 will both have two addresses. One set of those addresses share a subnet and by virtue of longest prefix match will be the pair picked by the source/destination address selection rules. So host1 and host2 will happily communicate without needing to traverse a router.
In other words: it is quite all right for nodes to have a 6to4 pseudo-interface enabled even if another link to which they are connected has a native prefix including those within 2002::/16. The RFC is fine as is. --Brian > -----Original Message----- > From: Michel Py [mailto:[EMAIL PROTECTED] > Sent: Thursday, 27 March, 2003 12:14 > To: Ole Troan > Cc: Brian Carpenter; [EMAIL PROTECTED] > Subject: RE: 6to4 and 2002:PRIV:ATE [RE: A use for site local > addresses?] > > > > Ole Troan wrote: > > a host connected to a native link should not > > automatically enable a 6to4 pseudo interface. > > Agree, and especially not if this native link RAses a prefix > within 2002::/16. > > > > Brian Carpenter wrote: > > Some hosts can support such a pseudo-interface, but having > > it on by default is a problem IMHO. > > RFC 3056 mainly talks about routers and strongly implies > > what Michel says, but that MUST NOT is not in any RFC. > > It should be, but is implied anyway because that's the only > way it can work. > > Example: My IPv4 prefix is x.y.z.0/24 > I have four subnets: > - x.y.z.0/26 > - x.y.z.64/26 > - x.y.z.128/26 > - x.y.z.192/26 > > My router is x.y.z.1 and x.y.z.65 and x.y.z.129 and x.y.z.193 > host1 is x.y.z.66 host2 is x.y.z.67 > > I migrate to IPv6 using 6to4. I decide that my IPv6 prefix is > 2002:xxyy:zz01::/48. Makes sense as the router is going to be > the 6to4 gateway for the site. > > I will dual-stack. My subnets now are: > > Routing prefix|Site|IID > |topo| > - x.y.z.0/26 2002:xxyy:zz01:0000::/64 > - x.y.z.64/26 2002:xxyy:zz01:0001::/64 > - x.y.z.128/26 2002:xxyy:zz01:0002::/64 > - x.y.z.192/26 2002:xxyy:zz01:0003::/64 > | | > > > My hosts IPv6 addresses should be: > > Routing prefix|Site|IID > |topo| > host1: 2002:xxyy:zz01:0001:HST1:I:I:D/64 > host2: 2002:xxyy:zz01:0001:HST2:I:I:D/64 > | | > > > However, if there is a 6to4 interface enabled on the hosts, > it breaks thinks as the hosts might decide to use: > > Routing prefix|Site|IID > |topo| > host1: 2002:xxyy:zz66:????:HST1:I:I:D/64 > host2: 2002:xxyy:zz67:????:HST2:I:I:D/64 > ^^| | > || > ?? > > Not only this is not what I want but it does break things as > these two hosts are not even in the same IPv6 logical subnet > with the 6to4 address they pick. If these two hosts need to > talk together they need to transit by the router, no good. > > In other words: the fact that the RFC does not mention that > hosts must not have a 6to4 pseudo-interface enabled if the > link has a native prefix including those within 2002::/16 > does not change the reality that 6to4 interfaces on hosts > break things so using them is not an option unless there is > only one host per site. > > Michel. > > > -------------------------------------------------------------------- > IETF IPng Working Group Mailing List > IPng Home Page: http://playground.sun.com/ipng > FTP archive: ftp://playground.sun.com/pub/ipng > Direct all administrative requests to [EMAIL PROTECTED] > -------------------------------------------------------------------- > -------------------------------------------------------------------- IETF IPng Working Group Mailing List IPng Home Page: http://playground.sun.com/ipng FTP archive: ftp://playground.sun.com/pub/ipng Direct all administrative requests to [EMAIL PROTECTED] --------------------------------------------------------------------
