> 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.
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