Does Asterisk perform IP blacklisting?

Hi all.

Every time my Asterisk server reboots, any SIP telephone within a list of specific brand and models isn’t able to register with Asterisk until its IP address is changed to one that doesn’t belong to the pool of IP addresses previously assigned to one of the currently concerned devices.
The outcast IP address become again available after some time has passed, usually one or more days.

Let’s say, for instance, that I have ten SIP telephones with IP addresses 192.168.1.x with x=1 to 10, to fix the issue when it occurs I must assign to the telephones new IP addresses not belonging to the previously used range, for instance: 192.168.1.x with x=11 to 20.

It looks to me as if Asterisk writes the concerned IP address in a sort of “IP blacklist” due to some, I presume, telephone’s misbehaviour.

A packet trace of the exchanges between the telephone with the blacklisted IP address and the Asterisk server shows that Asterisk doesn’t respond to any and all requests coming from the concerned device as long as its IP address is unchanged.

I’m using Asterisk 1.4.36 within Elastix 1.6.2 on a CentOS 5.8 64-bit architecture.

I would like to know how to fix it and, if the IP blacklist indeed exists, how to clear it by hand.



No, although many people add third party blacklisting software, like “fail2ban”.

Well, honestly I don’t know where to start from in order to collect the data needed to investigate the issue and all the advice in this respect is very welcome.
The crucial moments being just at the start of Asterisk, I guess, it may take some special/sophisticated probes to collect the needed data.

What I know about the issue is:

  1. The issue happens typically after the Asterisk server reboots,
  2. It happens with at least two SIP telephone brands - they are the only two brands I’ve been using so far,
  3. It doesn’t happen with all the models of the same brand,
  4. For one brand the impacted models are the more recent ones,
  5. While the phone can’t receive calls, it can be used for outgoing calls,
  6. When the issue happens, each registration request packet is totally ignored by Asterisk, i.e. it doesn’t receive any reply packet, not even to say what’s wrong,
  7. On occasions, certain concerned extensions manage to register after one, two or more hours from re-boot.
    They’re all the facts I know.