Problem: I was unable to update Quickbooks Pro 2006 from behind my PIX 501 corporate firewall. The error I received was 12007. I called Quickbooks support and spoke with three individuals; none were able to fix the problem. I tried everything available in Quickbooks support site as detailed in the links below.
Finally, I noted the following log entry on my PIX 501 Firewall when trying to update Quickbooks 2006 Pro on any computer in my office:
410001: Dropped UDP DNS reply from outside 206.154.105.67/53 to inside:192.168.1.20/9362; packet length 526 bytes exceeds configured limit of 512 bytes
What happens? The computer in our office makes a DNS query to a Quickbooks server. The server replies with a packet that is larger than the maximum size allowed on a Pix Firewall default configuration. To bypass this limit, "fixup" on the DNS protocol can be disabled. You may be able to increase the maximum packet length but I did not try this. Why Quickbooks DNS communication is different from every other application we run is beyond me.
Run this command in Terminal Configuration mode: no fixup protocol dns maximum-length 512
After this change was made, the computers updated Quickbooks successfully