[Kea-users] [EXTERNAL] Re: Need to have DHCP Relay in order for Kea to work...?
DDFR | Ronald Blaas
ronald.blaas at ddfr.nl
Tue Jul 23 07:00:56 UTC 2024
Hi,
From what I am seeing in the tcpdump.
The Client is getting an IP and acknowledge this
Look for the DORA process (Discover -> Offer -> Request -> Ack)
Looking in the dhcp-client_without_relay.txt I am seeing these steps.
So DHCP is working 🙂
How do you conclude that your client did not get an IP ?
As for the tcpdump with relay I did not see the DORA process. Only request and ack .
As for the server side tcpdump.. I was expecting to see the same DORA process.
Are there any other DHCP servers in your network? (please check)
Regards
Ronald
________________________________
From: Kea-users <kea-users-bounces at lists.isc.org> on behalf of Ubence Quevedo <thatrat at gmail.com>
Sent: Monday, July 22, 2024 12:54
To: Kea user's list <kea-users at lists.isc.org>
Subject: Re: [Kea-users] [EXTERNAL] Re: Need to have DHCP Relay in order for Kea to work...?
I tested over the weekend by turning the DHCP Relay off on the pfSense gateway, and did a tcpdump on both the client and the server.
I think I'm seeing the broadcasts from the client I was testing on the server, and it looks like the client is receiving the response, but the IP isn't getting assigned to the system.
This is illustrated in the traffic from dhcp-client_without_relay.txt and dhcp-server_without_relay.txt.
As soon as I turned the DHCP Relay back on, the client properly got an IP address which is illustrated in dhcp_with_relay.txt.
Maybe I have something misconfigured in my Kea conf? I'm a bit baffled by this since other broadcast traffic is working on my network.
Any thoughts on what I should be looking at next or checking in my Kea conf?
-Ubence
On Fri, Jul 19, 2024 at 4:18 AM Ubence Quevedo <thatrat at gmail.com<mailto:thatrat at gmail.com>> wrote:
Thanks for the response and the link, it is very helpful.
I'm seeing the DHCP relay traffic I would expect to see.
I'm going to test over the weekend disabling the DHCP relay and see what I see then.
-Ubence
On Thu, Jul 18, 2024 at 1:29 AM DDFR | Ronald Blaas <ronald.blaas at ddfr.nl<mailto:ronald.blaas at ddfr.nl>> wrote:
A yes I see.
You are using virtual interfaces.
This should work.
As for relay, no you do not need relay as the DHCP server is configured inside the same network.
Like suggested by others you need to run a tcpdump to see what/if packets are received by your dhcp server.
An example would be: tcpdump -i eno2.11 port 67 or port 68 -e -n -vv
(source<https://unixhealthcheck.com/blog?id=433>)
Should be run as root (or sudo)
You should see some traffic from machines requesting DHCP
regards
Ronald Blaas
________________________________
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>>
Sent: Wednesday, July 17, 2024 13:30
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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 the response.
Here are the interfaces configured on the server. eno2 is the main interface [untagged] and then there is eno2.11 and eno2.12 respectively for vlan 11 and 12:
eno2: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.10.3 netmask 255.255.255.0 broadcast 192.168.10.255
inet6 fe80::f604:def0:9990:a797 prefixlen 64 scopeid 0x20<link>
ether 50:eb:f6:4f:6c:2e txqueuelen 1000 (Ethernet)
RX packets 21002000 bytes 4720351435 (4.7 GB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 5775391 bytes 1207246387 (1.2 GB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 16 memory 0x51200000-51220000
eno2.11: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.11.3 netmask 255.255.255.0 broadcast 192.168.11.255
inet6 fd19:e769:2155:aa4a:2ca5:722f:5815:fd88 prefixlen 64 scopeid 0x0<global>
inet6 fd19:e769:2155:aa4a:8123:1ebe:15d1:88a1 prefixlen 64 scopeid 0x0<global>
inet6 fe80::1b5:af43:403b:d5d7 prefixlen 64 scopeid 0x20<link>
inet6 fd19:e769:2155:aa4a:8997:46a6:a4fc:ddbc prefixlen 64 scopeid 0x0<global>
inet6 fd19:e769:2155:aa4a:83de:c6c8:c181:5dbe prefixlen 64 scopeid 0x0<global>
inet6 fd19:e769:2155:aa4a:596c:3610:d7b4:1d18 prefixlen 64 scopeid 0x0<global>
inet6 fd19:e769:2155:aa4a:a2ed:50cf:5609:5e0e prefixlen 64 scopeid 0x0<global>
inet6 fd19:e769:2155:aa4a:bcfe:867f:4dc:c8f8 prefixlen 64 scopeid 0x0<global>
inet6 fd19:e769:2155:aa4a:14a6:e870:b2ad:d2d9 prefixlen 64 scopeid 0x0<global>
ether 50:eb:f6:4f:6c:2e txqueuelen 1000 (Ethernet)
RX packets 5820439 bytes 1191558319 (1.1 GB)
RX errors 0 dropped 11 overruns 0 frame 0
TX packets 2733488 bytes 637055127 (637.0 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
eno2.12: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.12.3 netmask 255.255.255.0 broadcast 192.168.12.255
inet6 fe80::fda3:7df7:98b0:d9e6 prefixlen 64 scopeid 0x20<link>
ether 50:eb:f6:4f:6c:2e txqueuelen 1000 (Ethernet)
RX packets 7737728 bytes 1816607005 (1.8 GB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 529891 bytes 125658614 (125.6 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
My interfaces in kea-dhcp4.conf are configured like:
"interfaces": [ "eno2/192.168.10.3<http://192.168.10.3/>","eno2.11/192.168.11.3<http://192.168.11.3/>","eno2.12/192.168.12.3<http://192.168.12.3/>" ]
This is why I'm a little baffled why I need the dhcp relay since all of the interfaces should be listening on each vlan but aren't picking up the traffic.
Routing has been an issue on my network, which is related to another post I'm going to make later with bridged interfaces and dhcp requests from VMs to those bridged interfaces not getting IP addresses even though the server is receiving the request but the client isn't acknowledging them for some reason.
-Ubence
On Tue, Jul 16, 2024 at 11:52 PM DDFR | Ronald Blaas <ronald.blaas at ddfr.nl<mailto:ronald.blaas at ddfr.nl>> wrote:
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
________________________________
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>>
Sent: Tuesday, July 16, 2024 13:04
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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_190cab5a40c4cff311]
From: Kea-users <kea-users-bounces at lists.isc.org<mailto:kea-users-bounces at lists.isc.org>> On Behalf Of DDFR | Ronald Blaas
Sent: Monday, July 15, 2024 2:15 AM
To: kea-users at lists.isc.org<mailto:kea-users at lists.isc.org>
Subject: [EXTERNAL] Re: [Kea-users] Need to have DHCP Relay in order for Kea to work...?
You don't often get email from ronald.blaas at ddfr.nl<mailto:ronald.blaas at ddfr.nl>. Learn why this is important<https://aka.ms/LearnAboutSenderIdentification>
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
________________________________
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>>
Sent: Monday, July 15, 2024 00:26
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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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