fred at cisco.com
Sat Sep 6 00:30:35 CEST 2008
On Sep 5, 2008, at 3:09 PM, david.freedman at uk.clara.net wrote:
> Is there any good reason why I shouldn't be filtering the ULA
> range at the edge (FC00::/7) ?
You should *absolutely* be filtering the ULA range of prefixes from
you customers unless you have an agreement to do otherwise, and then
you should implement that agreement. There are some strictures on the
form of the agreement; if a network agrees to share a ULA with another
network, it should be shared between those networks and not with
others. In general - and if I were writing a contract that permitted
ULA exchange I would include this in the contract - I would expect an
ISP to refuse all ULA prefixes from customers and expect customers of
ISPs to share ULAs over some form of VPN or private connectivity.
If you don't do that, a ULA is a random prefix that a network decided
to use, and may conflict with some other network that randomly picked
the same prefix. Think about it...
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