pfSense uses its internal routing table to determine the route to DNS servers (remember that policy-based routing does not apply to traffic generated by pfSense). As a result, if static routes are not configured, then pfSense will only use the primary WAN interface to access DNS servers. Therefore, you must configure static routes if you want pfSense to use the correct OPT_WAN interface for DNS queries. If you do not configure static routes for the OPT_WAN interfaces, there are two issues:
- If you are using your ISP's DNS servers, often ISPs will block recursive DNS queries from outside their network. This problem can be eliminated if you use alternative DNS servers such as the ones operated by OpenDNS.
- If no static routes ...
