Re: how is the MAC for tap(4) computed?
ill...@gmail.com wrote this message on Mon, Nov 04, 2013 at 16:08 -0500: On 4 November 2013 12:09, Dan Nelson dnel...@allantgroup.com wrote: In the last episode (Nov 04), Aryeh Friedman said: There seems to be a very high rate of MAC address collisions when tap is running on different machines is there anyway to make the selection of MAC more random It looks like it's generated based on the number of ticks since boot, plus the unit number of the tap device: http://fxr.watson.org/fxr/source/net/if_tap.c#L434 So if you have devices created on boot on a bunch of machines, chances are high that you'll get conflicts. Maybe instead of using the 'ticks' value, kern.hostid could be used instead? That has much better randomness than 'ticks'. With physical interfaces you can use something like ifconfig ath0 ether 00:2d:44:88:ff:00 (assuming the device the driver support changing MAC addresses) I've never tried it with a virtual interface, but it should work if the device supports it. But remeber when choosing an address like that, that you set the second low bit of the first octect to one to designate that it's a locally administered address... See wikipedia for more info: https://en.wikipedia.org/wiki/MAC_address#Address_details -- John-Mark Gurney Voice: +1 415 225 5579 All that I will do, has been done, All that I have, has not. ___ freebsd-virtualization@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-virtualization To unsubscribe, send any mail to freebsd-virtualization-unsubscr...@freebsd.org
Re: how is the MAC for tap(4) computed?
Hi Aryeh, There seems to be a very high rate of MAC address collisions when tap is running on different machines is there anyway to make the selection of MAC more random Do you mean, tap(4) when used with bhyve ? If so, bhyve calculates the MAC address for adapters based on an md5 hash of the PCI slot/function and VM name. If you use the same bhyve configuration on a different machine, the MAC address will be the same. If that's the problem, you may want to supply your own MAC address with the mac= parameter on the command line e.g. later, Peter. ___ freebsd-virtualization@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-virtualization To unsubscribe, send any mail to freebsd-virtualization-unsubscr...@freebsd.org
Re: how is the MAC for tap(4) computed?
In the last episode (Nov 04), Aryeh Friedman said: There seems to be a very high rate of MAC address collisions when tap is running on different machines is there anyway to make the selection of MAC more random It looks like it's generated based on the number of ticks since boot, plus the unit number of the tap device: http://fxr.watson.org/fxr/source/net/if_tap.c#L434 So if you have devices created on boot on a bunch of machines, chances are high that you'll get conflicts. Maybe instead of using the 'ticks' value, kern.hostid could be used instead? That has much better randomness than 'ticks'. -- Dan Nelson dnel...@allantgroup.com ___ freebsd-virtualization@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-virtualization To unsubscribe, send any mail to freebsd-virtualization-unsubscr...@freebsd.org
Re: how is the MAC for tap(4) computed?
On 4 November 2013 12:09, Dan Nelson dnel...@allantgroup.com wrote: In the last episode (Nov 04), Aryeh Friedman said: There seems to be a very high rate of MAC address collisions when tap is running on different machines is there anyway to make the selection of MAC more random It looks like it's generated based on the number of ticks since boot, plus the unit number of the tap device: http://fxr.watson.org/fxr/source/net/if_tap.c#L434 So if you have devices created on boot on a bunch of machines, chances are high that you'll get conflicts. Maybe instead of using the 'ticks' value, kern.hostid could be used instead? That has much better randomness than 'ticks'. With physical interfaces you can use something like ifconfig ath0 ether 00:2d:44:88:ff:00 (assuming the device the driver support changing MAC addresses) I've never tried it with a virtual interface, but it should work if the device supports it. -- -- ___ freebsd-virtualization@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-virtualization To unsubscribe, send any mail to freebsd-virtualization-unsubscr...@freebsd.org
