We are a small library and are trying to switch our ISP, but after the switch we have VPN and SIP failures. We have a DSL modem set up in bridge mode, we have a Juniper firewall, and Windows Server 2003 (an upgrade is in progress on that one). The process begins with importing a new config file into the firewall (Juniper support has confirmed these settings are correct). Logging into Network Solutions and updating our A Record under advanced DNS settings with the new IP address provided to us by Century Link, for our web site and VPN, etc.
After the updated IP takes effect, we have full functionality for a short time our Book Mobile can use VPN and we have a user from home that can use VPN. However after a short time we start to have failures, if the Book Mobile disconnects from the VPN they can not reconnect and Home User has the same problem ending up with a "691 error failure to authenticate" Our Laptop vending machine can not connect with the SIP, our video game dispenser will have SIP connect issues as well.
The last two times we have attempted the switch we had to change back at the end of the day because we can't figure out the problems, cannot pin point where the issue is stemming from.
A little history is that the servers, website redirect, VPN among other things were set up by our former IT company that was let go because of unprofessional behavior, this was before I started, so we can't ask them for help if we wanted to.
I was thinking it might be a proxy setting somewhere on our web server where our VPN connections live. But I couldn't find one. I did find in our DHCP setting under Scope Options an IP address listed after the IP address of our server 188.8.131.52, which is also listed on the NIC as an alternate DNS under the TCP/IPv4. So I tried to change this DNS setting to Google's 184.108.40.206 instantly we got a VPN failure. When I switched it back we have VPN connects right away.
So my question is why are we using a Level 3 DNS, why does this affect the VPN, and what can we do during the next switch over attempt to resolve this issue?