ISC DHCP Server Custom DHCP Options 252 for WPAD prevents DHCP Static Mappings custom DNS

aGeekhere

Hi when you use Custom DHCP Options 252 String "http://192.168.1.1/wpad.dat" users with DHCP Static Mappings and custom DNS no longer use the custom DNS and are overridden to use the defaults set in DNS Server Settings.

Could be related to https://redmine.pfsense.org/issues/3915

This was working correctly in pfsense 2.7.0 (using 2.7.2 now)

To test set the following
System General Setup DNS Server Settings
1.1.1.1

Services DHCP Server LAN
Custom DHCP Options
252
String
"http://192.168.1.1/wpad.dat"

Create a static map for an ip address and give it a custom dns for 8.8.8.8

Note you can use the WPAD package to test https://forum.netgate.com/topic/116163/unofficial-wpad-package-for-pfsense-software

You can use https://dnsleaktest.com to test which dns server it is using

Any work arounds ? Kea DHCP does not seem to have the Custom DHCP Options for the WPAD

UPDATE 1:
Same issue if you use Host Overrides in DNS Resolver

wpad	pfsensedomain.local	192.168.1.1	WPAD Host Override

UPDATE 2:
Same issue when using Kea DHCP with WPAD Host Overrides in DNS Resolver

Gertjan

@aGeekhere said in ISC DHCP Server Custom DHCP Options 252 for WPAD prevents DHCP Static Mappings custom DNS:

UPDATE 1:
Same issue if you use Host Overrides in DNS Resolver

Host override ?
Can't work, as you told the device to use 8.8.8.8 as a DNS source. The pfSense resolver will no be used by that device.

Create a static map for an ip address and give it a custom dns for 8.8.8.8

@aGeekhere said in ISC DHCP Server Custom DHCP Options 252 for WPAD prevents DHCP Static Mappings custom DNS:

UPDATE 2:
Same issue when using Kea DHCP with WPAD Host Overrides in DNS Resolver

kea, right now, doesn't allow you to add any DHCP options like "option 252". If you need these, stay with ISC.

Btw https://redmine.pfsense.org/issues/3915 was solved a decade ago.

aGeekhere

@Gertjan
Here is what happens
if i use ISC DHCP with Custom DHCP Options the static map with the custom DNS stop working and uses the DNS in general setup (proxy still works)

If i remove the Custom DHCP Options and just use Host Overrides in DNS Resolver while using Enable Forwarding Mode the static map with the custom DNS will stop working and use the DNS in general setup (proxy still works)

If i remove both the Custom DHCP Options and Host Overrides the static map with the custom DNS works and uses the custom DNS (proxy does not work, expected)

If i use Kea DHCP with Host Overrides in DNS Resolver while using Enable Forwarding Mode the static map with the custom DNS will stop working and use the DNS in general setup (proxy still works)

This works in pfsense 2.7.0 however it does not seem to in 2.7.2 as i have the old router that is on 2.7.0 to test on.

Gertjan

@aGeekhere said in ISC DHCP Server Custom DHCP Options 252 for WPAD prevents DHCP Static Mappings custom DNS:

if i use ISC DHCP with Custom DHCP Options

Check if it actually works. Go to packet capturing, enter/set this :

and click start.

You will see the DHCP client requests, and the pfSense DHCP server answer. The "Option 252" was send to the client ?