18.104.22.168/8 and /19s
smd at sprint.net
Sat Sep 23 22:25:43 UTC 1995
After much discussion with many different people,
including some at registries, I have modified our
filter-list to accept /19s in the 22.214.171.124/8 block.
The change will take effect upon the next clearing of
exterior BGP sessions with our various neighbours.
Note that there will be no further relaxtion of
the /19 limit, and that the principal reasoning
behind the change from /18 to /19 for this block
is as follows:
-- a miscommunication between me and various
registries several months ago which led
to registries and perhaps some providers
handing out some /19s that they honesty
expected would pass through the filters;
the fact that they did, to some extent,
due to the minor implementation glitch
on this side, exacerbated the problem.
-- several people have aggregated long prefixes
into /19s (thank you) and find that they
cannot reasonably do further aggregation
to /18s due to various allocation policies.
This change increases the number of prefixes AS1239 will
route towards by 129, all of which are /19s, and many of
which can and should be aggregated into even shorter
Note that this will not help anyone who is announcing
anything longer than a 19-bit prefix in the 126.96.36.199/8
range, nor anyone who is expecting to be able to
announce /19s in 188.8.131.52/8 - 184.108.40.206/8.
At this time, I don't intend to have AS1239 routers accept
/19s in those blocks from its external peers, nor do
I expect to increase the maximum length of the prefixes
accepted from 220.127.116.11/8 beyond that which registries
were allocating as part of their slow-start scheme
with the expectation that /19s probably were short
enough that they would stay routable everywhere.
Sean Doran <smd at sprint.net>
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