North American Network Operators Group
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Re: UUNet Offer New Protection Against DDoS

  • From: Patrick W.Gilmore
  • Date: Wed Mar 03 18:28:33 2004 
On Mar 3, 2004, at 5:51 PM, Lumenello, Jason wrote:


I struggled with this, and came up with the following.

We basically use a standard route-map for all customers where the first
term looks for the community. The customer also has a prefix-list on
their neighbor statement allowing their blocks le /32. The following
terms (term 2 and above) in the route-map which do NOT look for the
customer discard community, have a different standard/generic
prefix-list evaluation which blocks cruft and permits 0.0.0.0/0 ge 8 le
24.

By doing this, I only accept a customer /32 from his dedicated
prefix-list when it has the DOS discard community, otherwise I catch
them with the ge 8 le 24 in the following terms.
A lot of people seem to be doing this.

Mind if I ask what's the harm of letting customers announce /32 or /29s into your core as long as you filter at your borders?

The additional prefixes are not going to kill your routers, and it allows the customer more finely tuned traffic controls. IOW: Seems there is some utility and no harm.

--
TTFN,
patrick