dhcp Server issues

M

MCal27

New Member
Jul 25, 2025
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Hi Folks, sorry in abit of a panic here lol! Wasted two days on this issue so any help gratefully received!
I've setup two Proxmox 8 units (miniforum MS01's) both with a single windows server on for now (2025 and 2022) All seems to be working find apart from DHCP which is running on the 2022 server (though it was originally on the 2025 and it didn't work either) No clients on the network get a dhcp network slot. nothing. I know its not the network because when I enable dhcp on the router it broadcasts fine. I've disabled the firewall at the datacenter level and on the Server level too in proxmox. I've had a server 'expert' login and check my server configs (all fine). can anyone think of anything else at the proxmox level that could be causing this? I have my own Proxmox 7/ Windows server 2016 setup elsewhere and dhcp functions perfectly on there!

Thanks in adavnce. Al
 
Hi,

You should tell more about your setup, and especially your firewall rules and network setting (DHCP working on your router doesn't mean your network is fine, for example if you have DHCP-snooping enable on the router).

Best regards,
 
Well for a start I did say that the firewall is off. So I can take it that it can't be the PVE Firewall yes? unless I need to turn it off elsewhere beyond this?

Al
 

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Ok so I checked the router I'm using (An old Draytek 2830) and it doesnt support DHCP snooping. As I mentioned the setup is two minisforum MS01's both running PVE 8, and both with a single Windows Server VM (one on each). DNS seems fine, no errorrs, both Servers are DC's. DHCP shows no errors that I can see.
Right now both MS01's are connected into the Draytek, and a client W11 pc is also connected into a port on the draytek. The Clinet PC doesnt get DHCP. IF I give it a fixed IP & DNS (Server ip's) it works fine. I also tested wiith an iphone and USB-C Ethernet adapter. It too doesnt get an IP via DHCP. So I guess I'm assuming now that this is the Windows Server DHCP issue that appeared in June? But I dont see the affected updates as available to remove. So this let me to check here if it could be something on PVE?

Al
 
Hi,

Why did you touch the service ?
You should either disable it via GUI, or via cli
Code: 
pvesh set /nodes/{node}/firewall/options -enable false
and check via either GUI or CLI
Code: 
pve-firewall status && pvesh get /nodes/{node}/firewall/options

Have you tried a tcpdump on your DHCP server and your client to see if your server receives a request and emits a response ?

Best regards,
 
Last edited:
e;
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individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Sat Jul 26 10:24:01 BST 2025 from 10.184.68.22 on pts/0
root@pveone:~# cd /etc/pve/qemu-server
root@pveone:/etc/pve/qemu-server# cat 101.conf
agent: 1
bios: ovmf
boot: order=ide2;scsi0;ide0;net0
cores: 4
cpu: x86-64-v2-AES
efidisk0: local-lvm:vm-101-disk-0,efitype=4m,pre-enrolled-keys=1,size=4M
ide0: local:iso/virtio-win-0.1.271.iso,media=cdrom,size=709474K
ide2: local:iso/SERVER_EVAL_x64FRE_en-us.iso,media=cdrom,size=4925874K
machine: pc-q35-9.2+pve1
memory: 16384
meta: creation-qemu=9.2.0,ctime=1753354932
name: Server02
net0: virtio=BC:24:11:54:2E:AB,bridge=vmbr0
numa: 0
ostype: win11
scsi0: local-lvm:vm-101-disk-1,iothread=1,size=250G
scsihw: virtio-scsi-single
smbios1: uuid=3cd4c1d9-f31e-4def-a0a3-8166e95adfdf
sockets: 1
tpmstate0: local-lvm:vm-101-disk-2,size=4M,version=v2.0
usb0: host=4-1.4
vmgenid: 33dc3b3d-eba1-41e6-8e9f-58857377fbc2
root@pveone:/etc/pve/qemu-server#
 
well I've learnt that the issue MUST be proxmox 8.4, possibly in combination with the Minisforum ms01. I setup pfsense to function as a dhcp server..and it doesn't work either. No client machine gets any dhcp communication. I'll have to use an external dhcp source I guess. Pity I was really liking Proxmox too.
 
Hi,

does DHCP work inside proxmox (VM to VM) ?

Have you tried to tcpdump to check the network ?

Best regards,
 
I dont have time to create a test vm for checking if dhcp works within Proxmox sadly. But I'm setting up tcpdump now. never done it before :). thanks. I'll report back what I find
 
ok tcpdump scanning port 67 shows me this. Any help?
 

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Hi,

you should do the tcpdump inside your VM that act as DHCP as well, and use this filter
Code: 
tcpdump -i {INTERFACE} port 67 or port 68 -vv

This way we should see the exchange between the client and the server, and we need to see this inside the VM and HOST to see if this gets "stuck" inside the VM or make it through on your network.

Example produce :
Code: 
:~# tcpdump -i vmbr10 port 67 or port 68 -vv
tcpdump: listening on vmbr10, link-type EN10MB (Ethernet), snapshot length 262144 bytes
19:00:59.191646 IP (tos 0x10, ttl 128, id 0, offset 0, flags [none], proto UDP (17), length 328)
    0.0.0.0.bootpc > 255.255.255.255.bootps: [udp sum ok] BOOTP/DHCP, Request from bc:24:11:b1:5e:fa (oui Unknown), length 300, xid 0x5c123827, Flags [none] (0x0000)
          Client-Ethernet-Address bc:24:11:b1:5e:fa (oui Unknown)
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message (53), length 1: Request
            Requested-IP (50), length 4: 10.0.0.100
            Hostname (12), length 14: "administration"
            Parameter-Request (55), length 13:
              Subnet-Mask (1), BR (28), Time-Zone (2), Default-Gateway (3)
              Domain-Name (15), Domain-Name-Server (6), Unknown (119), Hostname (12)
              Netbios-Name-Server (44), Netbios-Scope (47), MTU (26), Classless-Static-Route (121)
              NTP (42)
19:00:59.192249 IP (tos 0x10, ttl 128, id 0, offset 0, flags [DF], proto UDP (17), length 335)
    10.0.0.254.bootps > 10.0.0.100.bootpc: [udp sum ok] BOOTP/DHCP, Reply, length 307, xid 0x5c123827, Flags [none] (0x0000)
          Your-IP 10.0.0.100
          Client-Ethernet-Address bc:24:11:b1:5e:fa (oui Unknown)
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message (53), length 1: ACK
            Subnet-Mask (1), length 4: 255.255.255.0
            Default-Gateway (3), length 4: 10.0.0.254
            Domain-Name-Server (6), length 8: dns.google,one.one.one.one
            Hostname (12), length 14: "administration"
            Domain-Name (15), length 11: "localdomain"
            Lease-Time (51), length 4: 3600
            Server-ID (54), length 4: 10.0.0.254
^C
2 packets captured
2 packets received by filter
0 packets dropped by kernel

Best regards,
 
And I see lots of traffic if I don't filter, so it seems to be working ok (wireshark). So surely as I thought the dhcp ports are blocked somehow by proxmox?
 

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