Proxy autodiscovery doesn't check DHCP (option 252)




Networking: HTTP
11 years ago
5 months ago


(Reporter: Fran Boon, Unassigned)


(Blocks: 2 bugs)

Dependency tree / graph

Firefox Tracking Flags

(Not tracked)


(Whiteboard: [necko-backlog])



11 years ago
User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv: Gecko/20060909 Firefox/
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv: Gecko/20060909 Firefox/

proxy autodiscovery can theoretically use either DNS or DHCP.
DNS is working perfectly for me.
DHCP is also working great for IE, but not for current Firefox (
Wireshark suggests that it isn't even checking for this feature (it looks for WPAD via DNS & WINS broadcast, but no DHCP INFORM which is what IE uses)

Reproducible: Always

Steps to Reproduce:
1.Configure Network for DHCP auto-proxy detection
2.Configure Firefox to use Auto proxy detection
3.Launch Firefox

Actual Results:  
No access to Internet (if direct access is blocked)

Expected Results:  
Proxy access configured according to PAC file

DHCP is setting the 252 option to:

(x.x.x.x is the IP of the Proxy server, port 80 is used by the proxy service, hence using 8080)


11 years ago
Component: Preferences → Networking: HTTP
Product: Firefox → Core
Version: unspecified → 1.8 Branch


11 years ago
QA Contact: preferences → networking.http

Comment 1

11 years ago
There is some code in attachment 121707 [details] [diff] [review] (see bug 28998), but it was never checked in.


9 years ago
Duplicate of this bug: 350759
Duplicate of this bug: 440547
Bug 444071 seems to be similar issue to this bug, and the bug opener of Bug 444071 says following in Bug 444071 Comment #8.
> using "Work offline", immediately followed by "Work online" indeed solves the problem!

To Fran Boon(bug opener): (same question as Bug 444071 Comment #6)
Can following be a workaround when the problem occurs?
  "Work offline", then return to "Work online" again.

Comment 5

9 years ago
Jo: As I recall, the WPAD implementation ignored DHCP.

Should we work on implementing that here? If so, lets make this NEW.

Then we need to find out if the DHCP implementation is OS-specific. If so, then we should make this a meta bug, and then create one bug per-OS implementation.

Fran: can you confirm the DHCP setting is changing (are you using ipconfig /all)?
Summary: Proxy autodiscovery doesn't check DHCP → Proxy autodiscovery doesn't check DHCP (option 252)

Comment 6

9 years ago

I have same problem. Can somebody repair it?
In our company is it problem and colleagues must manual setup web proxy server, but after that doesnt take in matter internal address exceptions...

Please look on it!
Thank you so much!

Comment 7

9 years ago
(In reply to comment #6)
> I have same problem. Can somebody repair it?
> In our company is it problem and colleagues must manual setup web proxy server,
> but after that doesnt take in matter internal address exceptions...

The DHCP option will return the location of the PAC-file : your colleagues should use that same PAC file when configuring their proxy-server, in the field 'Automatic proxy configuration URL', *not* the ipaddress of the proxy-server in the manual configuration. The PAC-file also contains those internal address exceptions.

If the PAC-file can be stored at the URL <> (replacing with the domain of your company), then you can also use the 'Auto-detect proxy settings' field, and it's even easier (it's also supported by Internet Explorer). The DHCP option is mainly used when the PAC-file can't be found at that particular URL, and the user needs some help in the automatic configuration. Unless the whole URL is configured manually ofcourse.

If you do not have a PAC-file at all, then you can't use the 'Automatic' or 'Auto-detect' settings at all, and neither can you use the DHCP option.

Comment 8

9 years ago
Thanks for answer!

I will try it, but it is not so much usable for all peoples... in every location they must change their proxy settings (yeah i know that exist proxy "changers"..)

Is really big problem to add this feature in Firefox?

Comment 9

9 years ago
btw: another problem is with Toolbars (icq, google, yahoo, so on...)

They dont accept configuration scripts or manual configuration...

Comment 10

8 years ago
This is the same problem I have. I can successfully use WPAD and auto detect in IE using DHCP, but not in Firefox. Can this be looked at? Auto proxy should support both methods.

Comment 11

7 years ago
Base on the advice from Jo Hermans comment in above, I have tried this and put in comments in Google Chrome bug's report as it is a similar problem.

Comment 12

6 years ago
At my company we use a multi-site, hierarchical web proxy model primarily for two purposes; first, to route users to a geographically local proxy for performance and bandwidth usage considerations, and second to even the load across our internet-connected web proxy devices. To accomplish this we utilize location-aware load balancing to direct users to a local web server to retrieve a location-specific version of the WPAD configuration file. This is a fairly complex configuration to maintain across >10 widely dispersed locations, and is flawed since the load balancing solution is limited in its ability to determine user locations (it is fairly broad). The proxy devices service both end-user web access and application web access, as well as B2B socks-based traffic. Legacy configuration on application servers make it difficult to reconfigure these servers to segregate user and application traffic on the proxy devices. We would like to use DHCP to replace our DNS-based solution for locating the WPAD configuration file, as all user desktops are configured to use DHCP. DHCP scopes are easily mapped to specific geographic locations which would enable more granular routing and load balancing. Unfortunately we cannot move forward with this solution because of this bug (and the same bug in Chrome). We would greatly appreciate this bug being resolved in a not-too-distant release. Thank you.

Comment 13

6 years ago
after more than 4 years still no answer about future implementation!

would be nice to see the feature to get option 252 into firefox - DNS is sometimes tricky and not possible to server!

Comment 14

6 years ago
It is disappointing to see that there is no update on this issue! I am now force to block Firefox on all office PC (all 100+ of them) due to the fact that we are deploying proxy that is being deployed via DHCP. Sad so sad!

Comment 15

6 years ago
Same here. Have to block 150+ Firefox users because the DNS-way of delivering WPAD is not currently possible in my company and Firefox still can't get wpad via DHCP.

Comment 16

6 years ago
Bumping up the status, which is not a promise that it would be fixed (I don't have anything to say over that). I noticed that Chrome has finally implemented support for this (Windows only !!!). The hard part is to support it on all platforms.
Ever confirmed: true

Comment 17

5 years ago
(In reply to fyrch from comment #15)
> Same here. Have to block 150+ Firefox users because the DNS-way of
> delivering WPAD is not currently possible in my company and Firefox still
> can't get wpad via DHCP.

The same for us. We can't use dns way because of company restriction.

Comment 18

5 years ago
Still no progress on this issue ? Resolving this issue is crucial for corporate users.


5 years ago
Blocks: 720362


5 years ago
Blocks: 350759

Comment 19

5 years ago
I'm too lazy to file a new bug and I just wanted to mention that after getting the PAC settings in network1, putting the computer in standby then waking it up in a PAC-free network2, firefox insists on using the other networks' proxy (which is unreachable, thus displaying the message that it cannot connect to proxy), even if I explicitly perform a dhcp release/renew. It only resumes working if I restart it.
firefox 12 beta, windows xp sp3

Comment 20

5 years ago
firefox version 11 and 12.0 does not receive Proxy auto-config file by DHCP 252

Comment 21

5 years ago
(In reply to bibl2008 from comment #20)
> firefox version 11 and 12.0 does not receive Proxy auto-config file by DHCP
> 252

What about version 13? Does anyone know if Mozilla is about to fix it?
Using proxy through auto-config file by DHCP is the only reasonable solution for companies using DirectAccess.

Comment 22

5 years ago
I'm using 14 beta and it still doesn't implement DHCP for WPAD.

This is a particular issue for us because our company is split between multiple geographical locations each with its own proxy server, but using a single DNS name for the internal domain. This makes using more difficult.

However, we already have the proxy info configured via DHCP for use by IE and Chrome.

If Firefox would support DHCP for proxy auto-detect, it would allow the browser to integrate into existing networks far easier and without having to manually configure each one to point to the .pac file.

Comment 23

5 years ago
Could anyone confirm version 17.0 (ESR) has fixed the lack of support for DHCP option 252?

Comment 24

5 years ago
No patch has been checked in (or even proposed), so how could it have been fixed ?
Equivalent Chromium bug (now fixed, on windows at least) is

Comment 26

4 years ago
(In reply to Daniel Veditz [:dveditz] from comment #25)
> Equivalent Chromium bug (now fixed, on windows at least) is

Seems like Firefox is the only important browser left that still won't support this feature. Is there a plan to finally assign this to someone?
This would be crucial to rollout Firefox in corporate networks!


4 years ago
OS: Windows XP → All
Hardware: x86 → All
Version: 1.8 Branch → Trunk

Comment 27

4 years ago
Any chances that this bug got some attention in near future?

Comment 28

4 years ago
The is a great increase in users demands for this feature inside vpn private networks. DNS Query for WPAD should not be the first inly thing to do for AutoDetect Proxy settings. Sometimes DNS Query for WPAD is not possible, because the pcs are not is a domain, or dns do not know the entry, or simply some routers does not relay the request

DHCP Comming first, before DNS, Firefox should check for option 252, in the dhcp settings, by requesting windows the DhcpRequestParams command. If windows has not requested the option252, a dhcpinform should be submitted to get the option. 

This is really important for trusted dhcp servers in private secured networks.

If of course firefox do not get the option 252 from windows, it should fallback to DNS WPAD METHOD.

But first we would like Firefox to implement correctly the DHCP WPAD METHOD


Comment 29

4 years ago
I have to say 'bye-bye' to firefox. I switched the browser of over 300 PCs in my corporate environment to Google Chrome and very satisfied with the outcome. 
I'm tired of the undefined waiting for this bug to be settled.

Comment 30

4 years ago
When this 7 years old bug will be fixed ? I use DHCP WPAD in a school environment with more than 500 computers, I would be glad to have this feature working on Firefox...

Comment 31

4 years ago
we exploit a network of ~1000 computers, the most part from which has firefox. It's really painfull for me, as software administrator, to maintain dns-wpad.
Please, please, fix it BUG and add dhcp-wpad method!

Comment 32

3 years ago
As another large corporation with tens thousands of computers, this is stopping us from implementing much more elegant and efficient solutions.  We are considering de-supporting firefox for our user base because of this...  PLEASE fix, or at least get some traction!  

Flags: needinfo?(nobody)

Comment 33

3 years ago
Firefox is not usable in corporate environment, forget about it and use IE
Flags: needinfo?(nobody)

Comment 34

3 years ago
(In reply to comment #31 and #32)
There is 2 solutions to meet your request : Either you paid an expert to path Firefox or your change the organization of your corporate network. ;) If no company pays to change Firefox, then Firefox will not be able to use in business.
Option 252 is for reserved private use:

It's Microsoft choice,

Unfortunatelly, DHCP hasn't an standard option for indicating de proxy.

DNS discovery must be used if you want to find the proxy:
Whiteboard: [necko-backlog]

Comment 36

5 months ago
I am thinking of working on this as it would help me out a lot. The link at the bottom of Josep's post now mentions DHCP.
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