Note
This seems to be unique to Mellanox interfaces only, or a combo with Mellanox + VF. Host where it is reproducible has: Mellanox Technologies ConnectX Family mlx5Gen Virtual Function [15b3:101e].
The issue cannot be reproduced on the same VM type deployed with VirtIO NIC.
Summary
When a DHCP client is configured on an interface, the settings for this interface are not applied at all.
How to reproduce
The configuration is:
set interfaces ethernet eth0 address 'dhcp' set interfaces ethernet eth0 address '172.20.17.91/25' set interfaces ethernet eth0 mtu '1500' set protocols static route 0.0.0.0/0 next-hop 172.20.17.1 set service ssh client-keepalive-interval '180' set service ssh port '22' set system console device ttyAMA0 set system name-server '1.1.1.1' set system option kernel cpu disable-nmi-watchdog set system option kernel cpu isolate-cpus '2-3' set system option kernel cpu nohz-full '2-3' set system option kernel cpu rcu-no-cbs '2-3' set system option kernel disable-hpet set system option kernel disable-mce set system option kernel disable-mitigations set system option kernel disable-softlockup set system option kernel memory hugepage-size 2M hugepage-count '1024' set system option reboot-on-upgrade-failure '5' set system syslog local facility all level 'info' set system syslog local facility local7 level 'debug' set vpp settings cpu corelist-workers '3' set vpp settings cpu main-core '2' set vpp settings interface eth0 driver 'dpdk' set vpp settings memory main-heap-size '1G' set vpp settings unix poll-sleep-usec '1000'
If a system is booted with this config, the whole process seems to look fine (no errors, warnings, etc.), and the interface itself is fully operable. But the actual config is not applied:
vyos@instance-20260116-1337:~$ show configuration commands | grep eth0
set interfaces ethernet eth0 address 'dhcp'
set interfaces ethernet eth0 address '172.20.17.91/25'
set interfaces ethernet eth0 hw-id '02:00:17:23:64:17'
set interfaces ethernet eth0 mtu '1500'
set vpp settings interface eth0 driver 'dpdk'
vyos@instance-20260116-1337:~$ show interfaces
Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down
Interface IP Address MAC VRF MTU S/L Description
----------- ------------ ----------------- ------- ----- ----- -------------
eth0 - 02:00:17:23:64:17 default 9000 u/u
lo 127.0.0.1/8 00:00:00:00:00:00 default 65536 u/u
::1/128
vyos@instance-20260116-1337:~$ show vpp interfaces
Kernel Dataplane Type IP Address MAC MTU State
-------- ----------- ------ ------------ ----------------- ----- -------
eth0 dpdk 02:00:17:23:64:17 9000 up
local0 local 00:00:00:00:00:00 0 down
eth0 tap4096 virtio 02:fe:03:30:c3:ab 1500 up