Simple remote phone blacklist issue

[cahollow]

Good morning everyone.

I'm having an issue with a simple remote phone that we have set up for a client.  This phone is frequently blacklisted and I'm having issues determining why this continues to happen.  I have another phone configured the same way (though with a different user/extension) here at my desk that will stay up and has never been blacklisted.

There are only a couple of differences of which I am aware.  One, the problem phone is at a users home where there is not a static IP (AT&T UVerse is the provider package) while our connection here at the office is a static IP.  The other difference is that my test phone is a VVX500 while the problem phone is a VVX600.

Will a changing IP trigger blacklist behavior?  I'm also having trouble locating documentation on exactly how this blacklist works, what documentation I have read says that the Blacklist Attack Threshold is triggered due to failed authentication attempts.  However, the problematic phone/user account has not had any password changes; as soon as I clear the blacklist entry it registers right away without further intervention. So I'm not sure how authentication fails unless these failures are being triggered due to the dynamic IP of this users connection.

[Anonymous · Accepted solution]

Colin, since this was resolved via a support ticket, I wanted to share the resolution so that others in the support community can learn from your experience:

It appears that when this is happening, the 7100 is receiving a REGISTER message from the phone without authentication, to which we reply with a 401 UNAUTHORIZED. The phone should then reply with a REGISTER message with authentication, but we do not receive that. Because we keep receiving the REGISTER messages without authentication, we eventually blacklist the phone. That could be caused by a number of things, I'll order from most likely to least likely:

1) Remote firewall is blocking 401 response to phone

2) Remote firewall blocks REGISTER message with authentication

3) Remote phone receives, but fails to respond properly to 401

4) 401 is dropped somewhere along the path between the 7100 and the phone

5) 7100 does not properly send 401 packet to phone

The problem was eventually traced to a wireless bridge on-site that was dropping traffic.

Thanks

[Anonymous]

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Thanks,

Jay