added note for including host's IP in client firewall

docs/content/guides/clients.md

@@ -61,6 +61,10 @@ Protocol specifiers (`/tcp` or `/udp`) require a port number. The following form
 - **Specified**: Only listed destinations are accessible (allow-only, everything else is blocked)
 - **Disable for specific client**: To disable firewall filtering for a single client while keeping it enabled for others, add `0.0.0.0/0, ::/0` to allow all traffic
 
+/// note
+To allow clients to reach the VPN server itself (e.g. for DNS), include the server's VPN address in the firewall allowed IPs.
+///
+
 **Use Case Examples**:
 
 - Allow only specific servers: `10.10.0.5`