Hi Scott.

>From what I am reading, the -m limit doesn't distinguish between IP
addresses and your example will actually drop the first 10 packets and then
it will be skipped for the rest of the second, so the rest of your rules
will apply.

"It is used to restrict the rate of matches, such as for suppressing log
messages. It will only match a given number of times per second..."

I'd suggest the recent module, which I use in the following way (to limit
incoming NTP requests to 20 packets per single IP during 60 seconds):

iptables -I INPUT -i eth0 -p udp --dport 123 -m recent --set
iptables -I INPUT -i eth0 -p udp --dport 123 -m recent --update --seconds
60 --hitcount 20 -j DROP

The recent module has some limitations on the number of addresses and
packets per address it remembers (with the defaults being 100 last
addresses and 20 packets per address).
You can increase those limits when loading the iptables recent module, some
more info on this here:
http://unix.stackexchange.com/questions/76271/iptables-recent-module

I have been using the recent module for a few years to filter NTP traffic
without problems.
Just make sure you don't cross the module limits (or adjust them).

Matej
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