Setting ignoreip in jail.conf to something wrong may lead fail2ban to think
that ignoreip = 0.0.0.0/0 was set!


Some times ago I set in my jail.conf:
ignoreip = 127.0.0.1/8,172.16.0.0/12

At this time no comment in configuration file told my that the IP/subnet list
has to be separted by spaces.

Today I found out that fail2ban don't care about any configured jails - nothing
happens when thousands of failed login attempts are done. After a long time of
troubleshooting I found out that the only change needed to be done was this:
ignoreip = 127.0.0.1/8 172.16.0.0/12

(reading /usr/share/doc/fail2ban/examples/jail.conf.gz give me the clue because
the comment above the ignoreip line told me to use spaces not commas)
without any worries - and behave like "ignoreip = 0.0.0.0/0".

Turing debugging level 4 on only gives this information:
2012-11-10 21:26:29,408 fail2ban.comm   : DEBUG  Command: ['set', 'ssh', 'addignoreip', '127.0.0.1/8,172.16.0.0/12']
2012-11-10 21:26:29,408 fail2ban.filter : DEBUG  Add 127.0.0.1/8,172.16.0.0/12 to ignore list

These lines don't give me any hint that something is going wrong here.

I think that behavior is a big surprise for any user. A very small failure
leads to a very big security hole - fail2ban silently stops working! (well, it
runs but just do absolut nothing)

I don't know the code but maybe there is better way for parsing this line which
would lead to a clear error message when starting fail2ban with such a
misconfigure line.