Standard prefix length filtering

Joe Provo nanog-post at
Wed Sep 19 14:45:07 UTC 2007

On Wed, Sep 19, 2007 at 09:03:35AM +0100, Andy Davidson wrote:
> On 19 Sep 2007, at 06:22, chk 543 wrote:
> >Is there a standard prefix length most providers filter on, or is  
> >there a way to find out what each provider filters on? We have been  
> >assigned a /22 and are wondering if we will have any issues with  
> >this block.
> There are no hard and fast rules, but a general rule is the more you  
> de-aggregate the more problems you are going to have, so unless you  
> have a very good reason not to, announce the /22 and nothing longer.

...and if you think you have "a reason" to do so, carefully consider
if the shorter prefix needs to be visibly globally or not.  If you
still are intent on deaggregating on a global scale and wish to
guarantee no problems, send the deaggregates in addition to the
aggregate such that you will still be visible to more-specific filters.



             RSUC / GweepNet / Spunk / FnB / Usenix / SAGE

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