The ProxySG returns a DNS error when attempting to connect to internal web servers
Network Error (dns_unresolved_hostname) Your requested host "<insert internal server name>" could not be resolved by DNS.
DNS is configured so the primary DNS servers accessed are external DNS servers.
The external DNS servers do not have the DNS mappings for internal resources
No alternate DNS configuration exists.
If the ProxySG is pointing to an external DNS server, then internal web servers may receive the DNS error described above. If you have a DNS server in your environment, you can do one of two things:
1.) You can make your internal DNS server the primary DNS server. Or
2.) You can add your internal DNS server as the alternate DNS server. That way if there is a DNS name resolution failure when the external DNS server is queried, then the alternate DNS server is queried. Please see 000010044 to see how primary and alternate DNS servers are handled/contacted.
To add the internal DNS server as an alternate DNS server, please launch the Management Console ( https://<ip.address.of.proxysg>:8082/ ) > Configuration tab > Network > DNS > Groups tab. There should be a listing for primary and alternate DNS servers. Highlight "alternate" and click on the Edit button. Enter the IP address of the internal DNS server. Click on the OK button and then Apply to save your changes. For additional information regarding DNS, please see the Configuration and Management Guide (CMG) for the version of SGOS you are running.
For SGOS 5.x, please see Volume 1: Getting Started; Chapter 7: Configuring DNS in the CMG. There are sections in the Configuring DNS section about adding DNS servers to the primary and alternate group.