Pingdom inaccurate results needs whitelisting - firewall rule update error

[actived]

Hi,
we use pingdom's free version to monitor whether our site is up/down.
It sometimes gives a series of 'server down' email alerts when the website can actually be reached quite normally.
It would be easy to write it off as a buggy service that gives wrong or inaccurate results, except for the fact that a lot of pingdom users seem to be very happy and sure that pingdom alerts are fairly accurate.

It seems that it is mostly a firewall issue - where if you have blocked an IP range due to some malicious activity from that region, and pingdom happens to have a server in that IP range, it reports a down alert as the ping is blocked.

These are the relevant links I found:
Simple tool to list Pingdom Probe IPs
Automatically update iptables rules for Pingdom monitors. | Personal blog of Chris Ergatides
Automatically update Pingdom firewall rules | MG IT Solutions

However when I tried out the last one - a script named update_pingdom_servers.sh, it gave a series of errors:

iptables: Bad rule (does a matching rule exist in that chain?)
iptables: No chain/target/match by that name

We are using csf+lfd as well and every blacklist entry in cphulkd is also entered into csf+lfd blacklist manually.

The alternative, as far as I understand would be to manually whitelist the IPs from the pingdom IP feed here: https://my.pingdom.com/probes/feed

Any pointers on how to fix this?

Any help is greatly appreciated.
Thanks in advance,
Dave

[cPanelTristan]

There's an option for CSF to enable dynamic IPs based on a hostname. You might consider using that instead. It's DYNDNS in the CSF configuration file.