Sprint's route filters and Europe

Alex.Bligh amb at xara.net
Mon Jun 3 16:52:37 UTC 1996

Daniel Karrenberg <Daniel.Karrenberg at ripe.net> wrote:

>   > with the result
>   > there are now likely to be 50% more adverts (i.e. 2x/19 and an additional
>   > /18 - /19 still necessary to get ANS to work as you can't put a /18
>   > route object in the database).
> Yes you can! If you have a /18 allocation you should announce it as such
> and put a /18 route object in the database. Can you be more specific
> on why it did not work for you?

Sorry I wasn't clear. If you have a /19 allocated in the RIPE database then
for obvious reasons you have to put a /19 route (not a /18) route in the
RIPE database. To get ANS to accept this you have to announce a /19 route
for this. This got filtered by Sprint.

Before Sprint's (much welcomed - thanks Sean) change of heart, you could
get around this if you were the lower /19 in the block by also making
a /18 advert. As the other half of the /18 was unused normally, this
makes no difference to anyone except those in the /19 suddenly get
Sprint connectivity. Actually it was likely to be of benefit to
any future holder of the upper half of the /18 as that would have
been the only way they would have gained Sprint connectivity (effectively
the holder of the lower half gives them partial transit to the point
where the upper /19 advert hits the /18 route to Sprint). This possibly
slightly naughty but oh-so-tempting hack would have meant that European
local IRs were likely to announce a /18 and a lower /19, and an upper
/19 rather than just two /19s. So Sprint would see one /18 and get
suboptimal routing, everyone else would see 3 adverts rather than 2.

Hope that makes sense.

Anyway, all sorted out now Sprint have changed their policy. Glad
the world has seen sense (i.e. RIPE and Sprint have agreed on the
same size - whether it was /18 or /19 didn't matter to me, just
as long as it was consistent).

Alex Bligh
Xara Networks

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