IPv6-Aware Helpers for PAC Routing Rules
Old PAC helpers and dotted-address patterns do not automatically become IPv6-aware when the proxy server gains an IPv6 address.
An IPv6-capable proxy listener does not make an old PAC rule IPv6-aware. Reaching the listener and correctly classifying the destination are separate requirements.
| Rule input | What to check |
|---|---|
dnsResolve, myIpAddress, isInNet in legacy examples | IPv4 address/mask assumptions. A false match on colon-separated data may mean unsupported input, not an outside-network destination. |
dnsResolveEx or isInNetEx | The client's support, required entry point and documented return format. |
Microsoft documents these IPv6-aware extensions. Every browser or WinHTTP consumer needs its own support check; one working client cannot establish compatibility everywhere.
A hostname may resolve to several addresses, and an extended helper can return a list. Interpret that documented list rather than compare its whole string as if it were one IPv4 address. Define outcomes for unsupported helpers, failed lookups and unexpected families.
If the policy is really about a company domain, a hostname rule may express it more directly than classifying every possible resolved address. Keep endpoint configuration and destination-rule evidence separate during diagnosis, so a successful IPv6 proxy connection does not hide a wrong PAC decision.