Hi,
Just wanted to post this as it took us awhile to spot the cause of the issue, may help someone else hours of work.
Issue - Proxy Auto Configuration over DHCP Relay doesn't work.
Setup - HQ has a UTM with a Microsoft DHCP Server (2012 R2). 4 RED sites in standard/unified mode. The 4 RED sites have clients that need to get IP addresses automatically from the DHCP server at HQ.
Detailed - If you wish to deploy the Proxy Auto Configuration to other sites whereby the clients get their IP address from a DHCP server over DHCP relay then you'll find it doesn't work yet they can get allocated a dynamic IP address absolutely fine.
Enabling DHCP Relaying and adding the networks to the interface of that does not automatically add the required firewall rule for Proxy Auto Configuration to work. You must still add a rule that allows these remote sites to use the service of DHCP to the DHCP server.
This is because the client computer does not pickup the Proxy Auto Configuration file when it requests an IP address at startup or at renew. It is called for when you load Internet Explorer. Looking at the firewall logs you'll see (if you haven't got the rule) that port 67 is denied when IE loads. Creating the rule allows this packet and therefore the Proxy Auto Configuration to work.
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