L-Root IPv6 address renumbering

David Soltero david.soltero at icann.org
Tue Mar 15 01:04:13 UTC 2016

Hi Job,

the following was posted earlier on another list ...

The rationale behind the renumbering is that the current IPv6 prefix,
2001:500:3::/48, comes as a direct minimum assignment. We were unable to
expand that allocation to a /47. What we (and I'm sure others) have
noticed is that ISPs and transit providers filter on allocation
boundaries, and constrain RIBs to the minimum allocation size. So our
reach for doing traffic engineering with a /48 is quite limited, noting
the first step in the BGP route selection state machine is generally the
prefix length.

The new address (2001:500:9f::42) sits in the prefix 2001:500:9E::/47,
which then allows us to get 'reach' of the more specific 2001:500:9F::/48
for traffic engineering purposes when we need it across the L-Root
constellation on IPv6.

We do this already on IPv4 using and

Hope this helps.

On 3/12/16, 5:05 PM, "Job Snijders" <job at instituut.net> wrote:

>Hi David,
>On Wed, Mar 09, 2016 at 09:06:20PM +0000, David Soltero wrote:
>> This is advance notice that there is a scheduled change to the IPv6
>> addresses in the Root Zone for the L root-server, also known as
>> L.ROOT-SERVERS.NET, which is administered by the ICANN.
>> The current IP addresses for the L.ROOT-SERVERS.NET service are:
>> 2001:500:3::42
>> As of March 23, 2016, the new IP addresses for the L.ROOT-SERVERS.NET service will be:
>> 2001:500:9f::42
>> The change will be implemented on the root zone on March 23, 2016
>> 2100UTC,  however the new address is already operational.
>Can you elaborate on why this change is being introduced?
>Kind regards,

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