Open Stack

 George,

 how often does it send the gratuitous ARP requests?

 Does it send it every time a network change is happening?


 Best,

 George


> You have to set two variables in the nova.conf file apparently
> ("send_arp_for_ha" and "send_arp_for_ha_count"):
>
> 
> https://github.com/openstack/nova/blob/3658e1015a2f7cb7c321cc1a0adfda37757fd80b/nova/network/linux_net.py#L764
> [4]
>
> On Fri, Mar 13, 2015 at 2:00 PM, Georgios Dimitrakakis  wrote:
>
>>> On 03/13/2015 05:54 AM, Georgios Dimitrakakis wrote:
>>>
>>>>> On 03/12/2015 06:24 PM, Georgios Dimitrakakis wrote:
>>>>>
>>>>>> Hello!
>>>>>>
>>>>>> I am facing a rather weird issue and would like to know if
>>>>>> anyone has
>>>>>> faced it before and the way you have solved it (if any).
>>>>>>
>>>>>> Firstly, I d like to let you know that I am running
>>>>>> Icehouse with Nova-Legacy
>>>>>> Networking.
>>>>>>
>>>>>> I have an application that launches and terminates VMs very
>>>>>> frequently and
>>>>>> automatically assigns to them
>>>>>> floating IP addresses.
>>>>>>
>>>>>> As a result if an IP has been used once then the second
>>>>>> time that is being used
>>>>>> cannot be reached for at
>>>>>> least 20minutes (this is the time frame if the newly
>>>>>> launched VM gets the same
>>>>>> IP address from one that
>>>>>> has just been terminated). Furthermore, this issue only
>>>>>> happens when the second
>>>>>> VM is launched on a
>>>>>> different physical node (hypervisor) than the first one.
>>>>>>
>>>>>> I believe that I have identified the problem to be ARP
>>>>>> Caching on the router
>>>>>> side since if I do:
>>>>>>
>>>>>> arping -U -I {Interface-Name} {IP-Address}
>>>>>>
>>>>>> in order to update the ARP Caches of the neighbors
>>>>>> immediately the new VM can be
>>>>>> reached on its floating
>>>>>> IP address.
>>>>>>
>>>>>> Is this the proper way of solving it?
>>>>>>
>>>>>> Can I somehow "instruct" OpenStack not to use the first
>>>>>> available IP address
>>>>>> everytime but on a random order
>>>>>> or the one that hasnt been used for enough time?
>>>>>>
>>>>>> Any other thoughts?
>>>>>
>>>>> Just a thought, have you tried enabling "send_arp_for_ha" in
>>>>> nova.conf?
>>>>>
>>>>> Chris
>>>>
>>>> Hi Chris! Thx for the feedback!
>>>>
>>>> send_arp_for_ha = True
>>>>
>>>> is already enabled in all nodes (controller and compute).
>>>>
>>>> Can I somehow verify that its working?
>>>
>>> You should be able to verify with a packet sniffer somewhere on
>>> your network.
>>>
>>>> How often is it sending the ARP request? Does it send it every
>>>> time nova configuration is changing?
>>>
>>> Im very much *not* an expert in this area, so Im afraid Im not
>>> the
>>> right person to ask about that.
>>>
>>> Chris
>>
>> Chris,
>>
>> thanks for the feedback. Any idea on what to sniff for?
>>
>> George
>>
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>
>
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> https://github.com/openstack/nova/blob/3658e1015a2f7cb7c321cc1a0adfda37757fd80b/nova/network/linux_net.py#L764
> [5] mailto:giorgis at acmac.uoc.gr