IPv4-mapped as ICMPv6 source address ?!

[Jared Mauch]

These are mpls devices that transport ipv6 but do not have ipv6 on the interface in question. They will also be dropped by loose rpf by a juniper device. 

Jared Mauch

On May 7, 2012, at 10:58 AM, Lutz Preßler <Lutz.Pressler at SerNet.DE> wrote:

> Hello,
> 
> doing traceroute6 www.ietf.org, I get
> [...]
> 5  2001:1890:1fff:109:192:205:34:181 (2001:1890:1fff:109:192:205:34:181)  95.902 ms  95.644 ms  119.383 ms
> 6  n54ny21crs.ipv6.att.net (2001:1890:ff:ffff:12:122:80:226)  175.058 ms  173.507 ms  176.317 ms
> 7  cgcil22crs.ipv6.att.net (2001:1890:ff:ffff:12:122:1:2)  171.525 ms  171.620 ms  172.789 ms
> 8  cr1.cgcil.ip.att.net (::ffff:12.122.2.53)  174.256 ms  174.761 ms  173.078 ms
> 9  sffca21crs.ipv6.att.net (2001:1890:ff:ffff:12:122:4:121)  172.066 ms  172.525 ms  174.842 ms
> 10  cr81.sj2ca.ip.att.net (::ffff:12.122.1.118)  171.342 ms  173.409 ms  171.158 ms
> 11  sj2ca401me3.ipv6.att.net (2001:1890:ff:ffff:12:122:126:238)  237.509 ms  170.582 ms  170.598 ms
> [...]
> and indeed see incoming ICMPv6 packets with ::ffff:/96 source addresses.
> I suppose, this is not as it should be. Does anyone know what kind
> of routers create those and in which situation (maybe if there are only
> link-local IPv6 addresses on the link)? Probably it's not SIIT.
> 
> Lutz