an effect of ignoring BCP38

Jo Rhett jrhett at
Thu Sep 11 03:07:52 CDT 2008

On Sep 11, 2008, at 12:59 AM, Pekka Savola wrote:
> A problem I have with these discussions is that everyone has their  
> own idea what "BCP38" implies.  Others say their loose-mode uRPF  
> setups are "BCP38".  Others are using strict uRPF or similar (e.g.  
> acls). Some think that Tier1 transit operators should apply one of  
> the options above to their tier2 customers.  Others think it should  
> just be applied at the site-edges.  Some don't consider spoofing  
> protection at LAN interface level at all, others call that also  
> BCP38.  Etc.

Honestly, *anything* is better than most of what's out there, which is  

> Loose mode URPF is seems (IMHO) pretty much waste of time and is  
> confusing the discussion about real spoofing protection.  The added  
> protection compared to ACLs that drop private and possibly bogons is  
> not that big and it causes transient losses when the routing tables  
> are changing.

I disagree.   But I will say that if everyone would apply strict mode  
or ACLs to their end point interfaces, this would likely make most of  
the loose mode irrelevant.

And your arguments about BGP changes affecting loose mode are only  
problematic on the busiest peering ports.  Loose mode works perfectly  
fine with zero drops (even on Cisco) on anything smaller than a full  
feed (ie, that ISP client of yours you do BGP with)

Jo Rhett
Net Consonance : consonant endings by net philanthropy, open source  
and other randomness

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