[ovirt-users] R: R: PXE boot of a VM on vdsm don't read DHCP offer

NUNIN Roberto Roberto.Nunin at comifar.it
Fri May 8 13:11:25 UTC 2015

Hi Dan
Thanks for answering

> Which kernel does the el7 host run? I think that Ido has seen a case
> where `brctl showmacs` was not populated with the VM mac, despite a
> packet coming out of it.

Kernel is: 3.10.0-123.20.1.el7.x86_64, package is vdsm only. Brctl isn't available within vdsm only package.
> Can you tcpdump and check whether the bridge propogated the DHCP offer
> to the tap device of the said VM? Does the packet generated by
> `ether-wake MAC-of-VM` reach the tap device?

Yes: host "see" the broadcast :
        0.000000            DHCP     346    DHCP Discover - Transaction ID 0x69267b67
It came from the right MAC:
        Source: Qumranet_15:81:03 (00:1a:4a:15:81:03)
And it is tagged correctly:
        802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 3500

This is the offer, on the bond interface:
        1.012355        DHCP     346    DHCP Offer    - Transaction ID 0x69267b67
Layer 2 info:
        Ethernet II, Src: Cisco_56:83:c3 (84:78:ac:56:83:c3), Dst: Qumranet_15:81:03 (00:1a:4a:15:81:03)
Tagging on the bond:
        802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 3500

The tag is correctly removed when DHCP offer is forwarded over the bond.3500.
Here's the offer content, seems everything right:

    Client IP address: (
    Your (client) IP address: (
    Next server IP address: (
    Relay agent IP address: (
    Client MAC address: Qumranet_15:81:03 (00:1a:4a:15:81:03)
    Client hardware address padding: 00000000000000000000
    Server host name:
    Boot file name: pxelinux.0
    Magic cookie: DHCP

Nothing of this offer appear on the VM side.

ether-wake -i bond0.3500 00:1a:4a:15:81:03 (started from the host)
reach the VM eth0 interface:
        2.002028   HewlettP_4a:47:b0     Qumranet_15:81:03     WOL      116    MagicPacket for Qumranet_15:81:03 (00:1a:4a:15:81:03)

Really strange behavior.


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