On 26 jul 2008, at 6:10, Pekka Savola wrote:
No, if there's no translator the packets won't end up at the destination because the mapped prefix isn't routed on the v6 internet.
If it's the destination address -- yes, but you might be surprised how widely default routes are being used. Enterprise-ISP egress use them a lot.
Right. But nobody configures mapped (or compatible) addresses on their host interfaces, and nobody puts them in their routers. So even if packets travel a long way by virtue of default routes, they're not going to be delivered to the right destination successfully unless there's a translator in the path that is set up to translate packets with these addresses.
The result is probably that packets end up looping between two routers at some ISP's backbone until the hop count rearches zero.
No, that generally happens when a customer has a prefix, such as a / 22, but they only use part of it, like a /23. If they then don't filter out packets to the unused space (the other /23) the packets will flow back to the ISP through the default route and the packets loop.
In this particular case ISPs won't send these packets to customers. They'll follow default routes until they reach a router that doesn't have a default or until the packets are filtered.
If it's the source address (it wasn't obvious whether this would be used, but apparently at least in translator->v6host direction), there is no check from this POV.
Right, from a translator to a host the packets could be delivered if they're not (ingress) filtered.
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