DHCP not behaving as expected

Hi,

I have an issue with dhcp which I cannot explain.

All my (Maas client) nodes are single nic 10GbE with ipmi sideband on this nic. For security reasons the ipmi is always configured on vlan 4044.

I created 2 scenarios, 1 works as expected, the other which I prefer doesn’t.
All tests are done on Maas 3.1 snap and Maas 3.2 snap.

Scenario 1:

  • A physical rackd (single nic)
  • untagged traffic for pxe/boot (10.10.15.0/24)
  • vlan 100 for regiond traffic
  • vlan 4044 for ipmi traffic (10.11.15.0/24)

When configured, it works as expected. With ps I look at the dhcp process and it shows:

/snap/maas/22134/usr/sbin/dhcpd -f -4 -pf /var/snap/maas/common/maas/dhcp/dhcpd.pid -cf /var/snap/maas/common/maas/dhcpd.conf -lf /var/snap/maas/common/maas/dhcp/dhcpd.leases ens1 ens1.4044

dhcp is listening on 2 nics, ens1 and ens1.4044, perfect

Scenario 2:

A vm as a rackd controller, vm has 3 nics

  • ens18 regiond traffic
  • ens19 pxe/boot (10.10.15.0/24)
  • ens20 ipmi (vlan is handled in the switch bridge) (10.11.15.0/24)

ens19 and ens20 both show up as untagged vlan in regiond, I configure dhcp the same as scenario 1

Now pxe/boot works, but ipmi dhcp not. With tcpdump I see the dhcp request from the ipmi/bmc coming in on ens20, but Maas is not servicing them.

With ps it shows:

/snap/maas/19835/usr/sbin/dhcpd -f -4 -pf /var/snap/maas/common/maas/dhcp/dhcpd.pid -cf /var/snap/maas/common/maas/dhcpd.conf -lf /var/snap/maas/common/maas/dhcp/dhcpd.leases ens19

dhcp is not servicing ens20, netstat -tulpn shows dhcp listening on 0.0.0.0:*

When I remove the dhcp scope for pxe/boot on ens19 I see:

/snap/maas/19835/usr/sbin/dhcpd -f -4 -pf /var/snap/maas/common/maas/dhcp/dhcpd.pid -cf /var/snap/maas/common/maas/dhcpd.conf -lf /var/snap/maas/common/maas/dhcp/dhcpd.leases ens20

Now ipmi works, but obviously pxe/boot not anymore

Why is dhcp not able to service 2 subnets in the same vlan? I have isc servers where this work for many nics at the same time.

Is my thinking wrong here?

Thanks