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Cisco PIX and Unity

Unanswered Question
Jun 20th, 2001
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I recently switched our LAN to a NAT/ Cisco PIX configuration. Before we had only a 3Com router and packet filtering. Its funny, after we switched over on a Friday night, everything seemed perfect (e-mail was flowing, stations were connecting) but I quickly realized that Unity voice mail was not working. You would here a person's greeting but get no 'tone' or 'beep' to leave you message. After hours of troubleshooting we came up with an answer. The new default gateway was the PIX router which was also doing NAT. It had a static NAT for our E-Mail server for Outlook Web Access. We notice when we ping the Exchange server from the Unity server by machine name, it was trying to resolve by external DNS servers. When the PIX saw the external IP address for the Exchange server, it basically thought, "hey, I have that address (static NAT) and did not send the packets on to the external internet for DNS resolution. It would just drop the packets. We added a static hosts file to the Unity box pointing to the Exchange machine and it's internal IP address and everything worked. The really strange thing about this is that we do not have hosts files on the Exchange server, or any other server for that matter. DOesn't the Exchange server also need to communication back to the Unity box. The other weird thing is when you ping the Untiy box from Exchange it by just the NetBIOS name (no FQDM) it would ping back with its internal IP address without a hosts file. When you pinged from Untiy to Exchange without the hosts file it tried to resolve the FQDM? (That is why it failed I guess) When the hosts file was configured it resolved the ping correctly and everything work. Weird? Why would one machine without hosts file try to resolve a ping to a NetBIOS name differently than the other?<br><br>

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