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Date: Thu, 29 May 2003 18:12:49 -0700 (PDT)
From: Neelkanth Natu <neelnatu@yahoo.com>
To: "."@babolo.ru, Paul Chvostek <paul@it.ca>
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cc: freebsd-net@freebsd.org
Subject: Re: ipfw rules vs routes to localhost?
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--- .@babolo.ru wrote:
> > I'm considering:
> > 
> >   ipfw add N deny ip from a.b.c.d to any
> > 
> > vs.
> > 
> >   route add -host a.b.c.d localhost
> > 
> > I need to block traffic to a number of IP addresses.  I thought I'd use
> > ipfw to avoid things like UDP DNS lookups that might come in ant take up
> > resources while my system tried to respond, but it's been suggested on
> > another list that setting routes to localhost will use less resources.
> > Ideally, I'd like to be able to block a few tens of thousands of IPs.
> > 
> > What's the scoop?
> ipfw with huge list works slow.
> Dont try huge route tables.
> 
> use in kernel:
> pseudo-device   disc            #Discard device (ds0, ds1, etc)
> 
> and
> ifconfig ds0 inet 0.0.0.1/32 (or else)
> route add -host a.b.c.d 0.0.0.1
> instead of localhost

An advantage of using "disc" is that you can monitor interface
counters and use tcpdump to see the discarded traffic. A blackhole
route to the loopback interface does not offer you this luxury.

best
Neel

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