[Kea-users] [EXTERNAL] Re: Need to have DHCP Relay in order for Kea to work...?

Wed Jul 17 06:51:44 UTC 2024

Hi

Not really sure what you mean here: "has one interface that I've setup with vlan interfaces"

Like what has been said before, either the DHCP server has an IP address in every IP subnet or you will have to make use of DHCP relay.

The DHCP server must know from which network the DHCP request is coming from.

As for logging, if there is nothing in the log you must have a routing problem (it is always routing 😋)

Ronald

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Subject: Re: [Kea-users] [EXTERNAL] Re: Need to have DHCP Relay in order for Kea to work...?

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Thanks for all of the responses on this.

The system that is the Kea DHCP server [an Ubuntu system] has one interface that I've setup with vlan interfaces.

I can access these other interfaces and verified through nmap that port 67 is open on all interfaces.

I can't seem to find any kind of ip helper option in the Unifi Controller [v8.2.93 running on a virtual Ubuntu system].

I've reconfigured the DHCP Relay on the pfSense to point to all of the interfaces, and I'm now seeing the traffic I'm expecting to see, which is fine since. understand a little better of what might be going on.

Just a little confused as to why the broadcast traffic for DHCP requests doesn't seem to be picked up on the vlan interfaces on the server.

I do have another question, but I'll put that in a separate post since it doesn't seem to be related to this question at hand.

-Ubence

On Mon, Jul 15, 2024 at 6:59 AM Joe Craig <JCraig at applieddigital.com<mailto:JCraig at applieddigital.com>> wrote:

Question about the setup. On the network switches that the DHCP requests would hit first, do you have IP Helpers configured? In my experience that’s what I’ve had to do to ensure that the packets make it to the DHCP server without a DHCP Relay. I’m in an environment where I cannot deploy a DHCP Relay service, so I am leveraging the IP Helpers on an L3 switch to forward those requests. This is passing through an Cisco firewall and all that. Hope that helps.

Thanks,

Joseph Craig
Systems Engineer
[cid:ii_190bb31a5f54cff311]

From: Kea-users <kea-users-bounces at lists.isc.org<mailto:kea-users-bounces at lists.isc.org>> On Behalf Of DDFR | Ronald Blaas
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Subject: [EXTERNAL] Re: [Kea-users] Need to have DHCP Relay in order for Kea to work...?

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Not really sure how you have your network setup.

But in my belief, if you want dhcp to work without RELAY you have to make sure your DHCP server is directly connected to all the LANs. So your DHCP server will need to have multiple Nics.

Is  there a particular reason you do not want to have a dhcp relay?

I have a kinda similar setup and am using DHCP relay. It is operating as expected and without problems.

It is also wise to share the output of your log file with the error you are receiving.

Tis helps in pinpointing the problem.

Regards

Ronald

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From: Kea-users <kea-users-bounces at lists.isc.org<mailto:kea-users-bounces at lists.isc.org>> on behalf of Ubence Quevedo <thatrat at gmail.com<mailto:thatrat at gmail.com>>
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Subject: [Kea-users] Need to have DHCP Relay in order for Kea to work...?

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Hi Everyone,

I’ve been using Kea for just under a year for a home setup on a Linux Ubuntu server.  I switched from isc dhcp since it was end of life.  My setup has a lot of MAC address reservations with some general pools for systems that don’t have IP reservations.

I also have a few vlans set up with the reservations for devices on each of the vlans.  I’m using pfSense as my gateway with some Unifi equipment that is vlan aware.

I’m running into an issue and I’m not sure why and would love some advice on how to look into this.

I have the interfaces on the system setup that is running Kea, to advertise on the untagged network [mostly some servers], vlan 11 [user systems], and vlan12 [IoT devices].

I don’t have the firewall in pfSense to block traffic between these networks yet, so they can all freely talk to each other.

Even though I have my Kea configured to advertise on all of the interfaces [untagged, 11, 12], I can’t seem to get anything to work unless I have the DHCP Relay service setup on the pfSense device to redirect all DHCP traffic to the Kea system’s untagged IP address [192.168.10.3].

I can verify through nmap that udp port 67 is running on all three interfaces.

If I turn off the DHCP Relay service, I was expecting the interfaces to pick up on the DHCP requests from devices on all of these networks.

This doesn’t happen and devices don’t get addresses.  I’ve even watched the logs I’ve split out and nothing is written for the duration that the relay service is turned off.  As soon as I turn it back on, I start seeing traffic again.

I’m running Kea 2.6.0.

I’d love to turn the DHCP Relay off to then try to troubleshoot another issue I’m having with bridging interfaces to VMs and then having the VM interface assigned to a vlan other than the bridged interface.  It seems to work for something else I’m doing, but just trying to rule some things out.  Probably another post if I can figure out why the DHCP Relay seems to need to be on.

Any ideas why I need the DHCP Relay service on another device even though all of the interfaces on each respective vlan are configured to listen for dhcp requests?

-Ubence

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