Re: [Softwires] MAP&4rd-U - DS routing replaced by v6-only routing in hub&spoke topology

Ole Trøan <> Tue, 07 February 2012 12:16 UTC

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Cc: Softwires WG <>, Wojciech Dec <>
Subject: Re: [Softwires] MAP&4rd-U - DS routing replaced by v6-only routing in hub&spoke topology
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> In a use case described in the 4rd-U draft (sec 5.3), an ISP replaces its dual-stack routing by IPv6-only routing.
> For this, independently from the number of IPv4 prefixes it has to support, it uses only one mapping rule.
> (By replacing each IPv4 route by an equivalent IPv6 route, it ensures that all customers keep their IPv4 addresses.)
> For this to work, the 4rd-U draft has a bit that, in the hub&spoke case, differs between CE-to-BR and BR-to-CE directions. Thus, packets sent to a CE take different routes depending on whether sent by a CE or a BR.
> I don't see how the equivalent could work with the MAP documents you edited.
> Is it that such a use case is out of scope for MAP?
> Or did I miss something?

injecting IPv4 routing into the IPv6 routing table is considered a bad idea. that was what caused Automatic tunnelling and IPv4 compatible address in RFC1933 to be deprecated.