vMX

Hi.

I am running (or trying to run) two vMX instances on the same KVM host. I have created two separate config files, where I have changed the MAC addresses under CONTROL_PLANE and FORWARDING_PLANE. However, but instances are using the same external bridge under BRIDGES.

When I start the first instance, the VFP is assigned the IP address I configured in the config file, but the VCP isn't assigned one at all. I checked to see if this was an issue with the dnsmasq configuration, and it doesn't seem to be. The file  /var/lib/libvirt/dnsmasq/br-ext.hostsfile includes entries for both the VCP and the VFP with the MAC addresses and IP addresses I configured in the configuration file.

When I start the second instance, the file /var/lib/libvirt/dnsmasq/br-ext.hostsfile is not updated at all. Hence, the second instance isn't assigned any IP addresses at all, since the DHCP server in dnsmasq knows nothing about the MAC addresses and therefor refuses to assign leases to them.

If I start the instances in a revesed order, the only effect is that the second instance is assigned IP addresses while the first isn't.

I searched through the forum and can see that quite a few of you are running multiple instances of vMX on the same host successfully. Is it just me that have experience this issue?

Could you share the output of 'virsh net-dumpxml br-ext'?

Sure thing!

This is the output of "virsh net-dumpxml br-ext" after both instances has been started (vmx1 first, then vmx2):

<network>
  <name>br-ext</name>
  <uuid>903829a7-1598-4c81-a653-1d9e2497d8d7</uuid>
  <forward mode='route'/>
  <bridge name='br-ext' stp='on' delay='0'/>
  <mac address='52:54:00:9f:a0:77'/>
  <ip address='172.16.0.1' netmask='255.255.255.0'>
    <dhcp>
      <host mac='0A:00:DD:C0:DE:0E' name='vcp-vmx1' ip='172.16.0.2'/>
      <host mac='0A:00:DD:C0:DE:10' name='vfp-vmx1' ip='172.16.0.3'/>
    </dhcp>
  </ip>
</network>

It looks exactly the same if i run the command before starting the second instance. I use the --install option to vmx.sh for both instances if that makes any difference.

About the FCP not supporting DHCP, I kind of figured that out since none of the FCP's got IP addresses. But I figure, if one VFP gets one, the other should too.

It seems br-ext was not properly updated while installing the 2nd vMX instance.

You may add vfp-vmx2 entity into it by using 'virsh net-update', see http://wiki.libvirt.org/page/Networking#virsh_net-update for instructions.

Here's a sample, you may replace the MAC/IP addresses with what you use.

sudo virsh net-update br-ext add ip-dhcp-host "<host mac='0A:00:DD:C0:DE:12' name='vfp-vmx2' ip='172.16.0.5'/>" --live --config 

In the meantime I will try to figure out the root cause.

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@szhong wrote:

You may add vfp-vmx2 entity into it by using 'virsh net-update', see http://wiki.libvirt.org/page/Networking#virsh_net-update for instructions.

 

In the meantime I will try to figure out the root cause.

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Brilliant, thanks. That will do for a workaround. I really appreciate it!

@szhong - I can replicate this issue - it seems if another vmx is running / if br-ext already exists, then the xml is not updated when the installer is run.

Contact me directly and I can DM you the details.

Hi Matt,

Thanks for reproducing this. I've indicated the root cause in my lab, we will fix it in future release.

/Simon

hi Simon / Matt,

I am facing same issue with vMX 17.2R1.13.  Can you please let me know work around for this issue ? 

thanks

Bhavesh

Just an addition. It's normal that VCP doesn't get address automatcally, because fxp0 doesn't support DHCP in 15.1F3.