So Philip Smith / Geoff Huston's CIDR report becomes worth a good hard look today

Dorian Kim dorian at
Thu Aug 14 06:23:12 UTC 2014

On Thu, Aug 14, 2014 at 01:47:20AM -0400, Dorian Kim wrote:
> On Thu, Aug 14, 2014 at 12:15:36AM -0400, Patrick W. Gilmore wrote:
> > Composed on a virtual keyboard, please forgive typos. 
> > 
> > > On Aug 13, 2014, at 22:59, Suresh Ramasubramanian <ops.lists at> wrote:
> > > 
> > > Swisscom or some other European SP has / used to have a limit where they would not accept more specific routes than say a /22 from provider x, so if you wanted to take a /24 and announce it you were SOL sending packets to them from that /24 over provider y.
> > > 
> > > Still, for elderly and capacity limited routers, that might work.
> > 
> > And Sprint used to filter on /19s outside swamp space. (See NANOG 1999 archives for my [wrong then corrected] interpretation of ACL112.) Etc., etc. 
> > 
> > For stub networks, especially ones who are not as performance sensitive, this can help extend the life of their routers. But not everyone can make AGS+s work for years past their useful life or get "-doran" IOS builds. The 6500 was first sold in 1999. I'm impressed it has lasted this long, even with new sups. Time to start thinking about upgrading. 
> Just as a historical note, Sprint didn't have AGS+ or such equipment that were being propped up by the /19 filters (at least for the vast majority 
> of the filter's existence). Neither did Verio. Those filters were primarily an attempt to enforce a certain behavior. 

It was kindly pointed out to me in private that my phrasing could be misleading here.

When ACL112 came into being, there were old equipment that were being protected by the /19 filters. However, the filters
were in place long after those equipment were replaced.


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