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Author Topic: How to configure DHCP Server to NOT assign a default gateway  (Read 4236 times)

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Offline smanders

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How to configure DHCP Server to NOT assign a default gateway
« on: January 22, 2013, 03:55:45 pm »
Hello,

I need pfsense to NOT assign a default gateway via DHCP.  I only want it to assign the IP address.  When I leave the field blank, the clients are still assigned the LAN interface's IP address as their default gateway ???.  This introduces a problem on my dual homed machines.  I even made sure the NIC in the Windows adapter binding order had my NIC that IS assigned a default gateway first in the list.  However, connections still are functioning properly until I remove the competing default route.

I found this old thread with no resolution.  I'm running the latest version of pfsense.  Any one know?

http://forum.pfsense.org/index.php/topic,33924.msg176092.html#msg176092

Thanks,
smanders

Offline johnpoz

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Re: How to configure DHCP Server to NOT assign a default gateway
« Reply #1 on: January 23, 2013, 01:45:37 pm »
Well if you read the text by the gateway entry you will see
    
"The default is to use the IP on this interface of the firewall as the gateway. Specify an alternate gateway here if this is not the correct gateway for your network. "

So that explains why leaving it blank does what it does - mine doesn't have an entry in it. 

If you look in /var/dhcpd/etc you will see the dhcpd.conf - in there you will see the option

 option routers 192.168.1.253;

Being set - where .253 is my lan interface IP, your will be what you set in the field or if left blank your interface the dhcp server is running on IP.

The dhcp server can be configured not to hand out that info - but it would have to be changed in the pfsense code to allow for that.  Submit a request to allow the option of not handing it out.

Most people running dhcpd on pfsense would want to hand out pfsense as the gateway I would have to assume.  If you don't want your dual homed boxes to use pfsense as gateway - just setup the IP on that interface on the client as static and don't set the gateway.

I wouldn't think it too hard of a change to make.. But I doubt too many people are asking for such a feature which is why it has not been setup as an option.
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Offline Willy

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Re: How to configure DHCP Server to NOT assign a default gateway
« Reply #2 on: February 28, 2013, 06:14:31 am »
I have (had) a similar problem. We have a separate VLAN for VoIP with QoS settings for the VoIP VLAN. Both the normal LAN and VLAN have DHCP. Some workplaces use a softphone. On these systems we set the normal LAN and the VLAN. Both get a IP from DHCP and both networks get a GW with the same metric. The problem is that Windows now randomly decides which gateway to use and Murphy will make sure it's always the wrong one.

I changed the pfSense code myself (services.inc, xmlparse.inc and services_dhcp.php) so I can check a checkbox to disable setting the gateway for that DHCP range. Problem solved until I upgrade to a new version I guess.

I really would like to see this feature in standard pfSense.

Offline johnpoz

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Re: How to configure DHCP Server to NOT assign a default gateway
« Reply #3 on: February 28, 2013, 07:48:56 am »
Well there you go submit your change then..  I would post up details in development section, or ask there how to get started with submitting code to pfsense.
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Offline Willy

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Re: How to configure DHCP Server to NOT assign a default gateway
« Reply #4 on: February 28, 2013, 10:34:58 am »
Well there you go submit your change then..  I would post up details in development section, or ask there how to get started with submitting code to pfsense.

I'm afraid my "hack" will not comply to pfSense coding rules, but I'll certainly have a look at it.

Offline johnpoz

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Re: How to configure DHCP Server to NOT assign a default gateway
« Reply #5 on: February 28, 2013, 12:35:54 pm »
Im sure if your hack works, it could be tweaked to align with standards..  There are couple of changes I make upon loading a new snap.. Just been too lazy to work out the details of how to get them put into the code myself.

Someone had created a patch to get vnstat2 working, which I have to reapply on each new snap.  Also I am not a fan of the local-ttl of 1 for dnsmasq..  I just don't see the reason to have such low ttl on my dns records..  They rarely if ever change, so I change it to 86400 in the services.inc file. 

Would like to see this as option to set this to whatever you want, etc.  Just too lazy to submit the code required to make it happen ;)  I will get to it sooner or later..  But if you have worked out the changes required to give you a check box - seems you got most of the work done already..  Be a nice addition that multiple people might take advantage of.
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Offline Derelict

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Re: How to configure DHCP Server to NOT assign a default gateway
« Reply #6 on: May 31, 2013, 12:34:48 pm »
Has this been formally submitted as an enhancement request?  A search on redmine for dhcp "default gateway" doesn't show one.

My scenario is I would like to NOT have a default gateway assigned to my workstation when I obtain a DHCP lease on my management VLAN. All I need is an interface on the right network.  All traffic not to the management VLAN should be routed out my main interface.

It would be nice to be able to suppress DNS Server assignment in the same fashion.
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Offline jimp

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Re: How to configure DHCP Server to NOT assign a default gateway
« Reply #7 on: June 03, 2013, 10:16:26 am »
There isn't a feature request for it that I've seen, but I have seen at least one other person ask for it. In order to not break anyone's existing installs, another option or keyword would need to be added.

So either:
1. A checkbox to suppress sending a gateway
or
2. Entering the word "none" into the gateway box will prevent the gateway from being supplied to clients.
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Offline gdo35

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Re: How to configure DHCP Server to NOT assign a default gateway
« Reply #8 on: November 14, 2013, 04:39:32 am »
Hello,

Old topic bu if it can help :
I manage to disable the default gateway assignment by DHCP server by setting the network address as default gateway.
For example I have a network 192.168.1.0/24, I set 192.168.1.0 as the default gateway.

pfsense accepts it but as the route is invalid it will not be used by the client.

It is a bite dirty but I hope it helps. ;)

gdo35