RRL outcome on legitimate traffic...

Lyle Giese lyle at lcrcomputer.net
Tue Dec 1 14:24:50 UTC 2020

You need to look at the reply named sends when it trips and starts 
limiting UDP traffic source from a given IP address.  It tells the 
requestor to try again using TCP instead of UDP.

So if the requestor is a legit dns server, it will retry using TCP and 
still get a valid answer.

Named does not blindly just drop traffic.

Lyle Giese

LCR Computer Services, Inc.

On 12/1/20 4:58 AM, Karl Pielorz wrote:
> Hi all,
> So there's been quite a thread - that originally started as "Bind 
> stats - denied queries" - and morphed into a whole discussion on 
> spoofed UDP, logging, RRL etc.
> In my original post - I never said the original traffic was likely 
> legitimate in anyway (just so we're clear - I didn't start that aspect 
> of that thread).
> So,
> Obviously RRL is pretty much all you can do with this stuff - 
> presumably, if someone throws a lot of queries that 'trip' the RRL - 
> but, say spoofed from another ISP's actual DNS servers/network - the 
> idea is that those IP's legitimate UDP queries will start getting 
> dropped :( - but the other ISP's DNS will then, hopefully switch from 
> UDP to TCP to get an answer?
> Looking at the distribution of rubbish we're seeing - I'm suspecting 
> some of the limits would have to be 'really low' to catch some of this 
> stuff (i.e. some times we just see 5 queries from an IP, and then 
> nothing for hours - even from within the same /24).
> Obviously the server can weather a quite a bit of this, and you can't 
> "block everything" (which is - in a circle, why I was asking 
> originally about getting stats for it :)
> Regards,
> -Karl
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