OSX - 'no route to host'

[Brandon Applegate <brandon () burn net>]

I've seen a few messages on this, but no decent replies or solutions.  In 
fairness, the most accruately scoped message wasn't on this list but 
rather a macports one:

http://lists.macosforge.org/pipermail/macports-users/2011-March/023882.html

On OSX (I have access to and have tested 10.6.8 + 10.7) nmap frequently 
reports 'no route to host' - specifically when I do a ping scan (-sP).

sendto in send_ip_packet_sd: sendto(4, packet, 40, 0, 192.168.64.5, 16) => 
No route to host
Offending packet: ICMP 192.168.64.21 > 192.168.64.5 Timestamp request 
(type=13/code=0) ttl=48 id=6230 iplen=10240
Sleeping 15 seconds then retrying

Sometimes it completes the scan on my home net /24 without fuss.  But most 
of the time it gets bogged down with the above.

I thought perhaps there was a sysctl doing some kind of ICMP rate limiting 
(and there is) - however tuning it to 0 didn't seem to have an effect.

Thanks in advance for any info.

--
Brandon Applegate - CCIE 10273
PGP Key fingerprint:
7407 DC86 AA7B A57F 62D1 A715 3C63 66A1 181E 6996
"SH1-0151.  This is the serial number, of our orbital gun."

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