[SOLVED] dhcp issue with KVM, LXC does not have the issue

[RobFantini]

Hello
we use pve enterprise repos all up to date.

dhcp server is isc-kea

we have fixed reservations set up at dhcp server based on mac address for some kvm's which are configured as dhcp clients in /etc/network/interfaces .
those kvms are not getting the reserved IP, instead they get an IP from the dhcp pool.

lxc does not have this issue.

I have been working on this for some hours . If anyone has a suggestion to fix or debug please send a communication .

Next I'll see if desktops have the same issue.

 

[RobFantini]

desktops do get a fixed reservation from the dhcp server.

 

[RobFantini]

i have a kvm which does get the correct address from dhcp.

/etc/network/interfaces :

# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

here is what a kvm which does not get the correct address has:

source /etc/network/interfaces.d/*
# The loopback network interface
auto lo
iface lo inet loopback
 
allow-hotplug eth0
  iface eth0 inet dhcp

 

[RobFantini]

so I installed network-manager on the kvm and eliminated the eth0 part of interfaces. still not solved
both systems are running debian bookworm .
and on the same vlan.

 

[RobFantini]

i moved the kvm to the same node as the one that gets correct address. that did not fix the issue.

 

[RobFantini]

I just tested a windows kvm, and it got the correct IP address from the dhcp server reservations.

next I'll try to test a non debian linux kvm

 

[RobFantini]

a centos kvm got the correct address.

so looks like a debian configuration issue

 

[wahmed]

The isc-dhcp-client is responsible on the Debian side to receive correct IP based on MAC. It is installed by default. But for some odd reason it is not:
apt install isc-dhcp-client

Tried to forcefully release and renew IP?:
dhclient -r <interface>
dhclient <interface>

Also check the content here to see if something is odd:
cat /var/lib/dhcp/dhclient.leases

With isc-dhcp-client, the interface simply receives the IP without fuss. It is as simple as it gets as you know.

 

[RobFantini]

Hello Wasim

# apt install isc-dhcp-client
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
isc-dhcp-client is already the newest version (4.4.3-P1-2).

# dhclient ens18
RTNETLINK answers: File exists

I think the issue is with kea-dhcp , or my configuration at kea-dhcp . It is strange that non debian systems do not have an issue.

Next I'll use this to try to see differences between centos and debian at the server using

sudo tcpdump -i eth0 port 67 or port 68 -e -n -vv

 

[RobFantini]

another question - is it possible to set the dhcp-relay for the pve vlans at the vmbr bridge or in network config? currently the relay is set at the switch which all the nodes are connected to.

 

[RobFantini]

this issue was caused by my deleting a couple of subnets from our network configuration system [ONA OpenNetAdmin IP Address Management (IPAM) system ] . after that the generated kea-dhcp4 configuration had some changes subnet id's ... so kea-dhcp say lease request coming in from a wrong network and rejected the request for a reservation. more detail is available at kea-users@lists.isc.org