- Original Message -
While building a virtual machine we ran into an error Not enough MAC
addresses left in MAC Address Pool. In the engine log I see this message.
2013-10-26 14:47:16,590 WARN
[org.ovirt.engine.core.bll.network.vm.AddVmInterfaceCommand] (ajp--127.0.0.
1-8702-12) [6fc05fa4] CanDoAction of action AddVmInterface failed.
Reasons:VAR__TYPE__INTERFACE,VAR__ACTI
ON__ADD,MAC_POOL_NOT_ENOUGH_MAC_ADDRESSES
2013-10-26 14:47:16,591 ERROR
[org.ovirt.engine.api.restapi.resource.AbstractBackendResource] (ajp--127.0
.0.1-8702-12) Operation Failed: [Not enough MAC addresses left in MAC Address
Pool.]
This led me to look at the engine config where I see these
MacPoolRanges: 00:1A:4A:97:5E:00-00:1A:4A:97:5E:FF version: general
MaxMacsCountInPool: 10 version: general
The MacPoolRange would seem to be the limiting factor here, cutting us off at
256 MAC addresses, which happens to be the number of virtual machine we
currently have. I assume that updating the MacPoolRange and restarting the
engine would resolve this issue. Has anybody experienced this issue? Why
would the pool size have 256 and the Max entry be set to 10, that seems
like a large difference.
Hi Thomas,
The MacPoolRanges is preset to what range was reserved initially when oVirt was
being developed.
Of course, in a LAN this doesn't make much difference as the possibility of MAC
hijack from a hardware vendor is extremely low.
The 3 first bytes in a MAC specify the vendor ID, and the 3 last bytes the
card address (explained in http://en.wikipedia.org/wiki/MAC_address ), so I'm
not sure why this was limited to 256 addresses but you can of course change the
limit.
I'm guessing it was set not to interfere with addresses used by libvirt that
you may have running in the LAN which use the same vendor ID.
Also please notice you can have multiple ranges separated by comma
e.g. MacPoolRanges:
00:1A:4A:97:5E:00-00:1A:4A:97:5E:FF,00:1A:4A:97:5F:00-00:1A:4A:97:5F:FF
Now the other value, MaxMacsCountInPool simply limits the MAC pool size so if
you have a pool that is too big the engine won't start.
So for example if you have pools
00:1A:4A:97:5E:00-00:1A:4A:97:5E:FF,00:1A:4A:97:5F:00-00:1A:4A:97:5F:FF it's OK
since there are 256 + 256 = 512 10 MACs
But, if you have pools
00:1A:4A:00:00:00-00:1A:4A:00:FF:FF,00:1A:4A:01:00:00-00:1A:4A:01:FF:FF it will
fail since there are 65536 + 65536 = 131072 10 MACs
Hope this helps,
Mike
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