From: Nicolas B. <nic...@ec...> - 2006-11-14 16:18:31
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Hi, I use UML with the tuntap virtual network driver. By default it uses ethernet fe:fd:xx:xx:xx:xx addresses. I asked google about those addresses with no success. Are these addresses allocated to anyone? Reserved for experimental use? Reserved for private use? Is it documented somewhere? Should I fear a potential conflict with other devices? Nicolas |
From: Jeff D. <jd...@ad...> - 2006-11-14 16:40:41
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On Tue, Nov 14, 2006 at 05:18:17PM +0100, Nicolas Boullis wrote: > I use UML with the tuntap virtual network driver. By default it uses > ethernet fe:fd:xx:xx:xx:xx addresses. I asked google about those > addresses with no success. > > Are these addresses allocated to anyone? Reserved for experimental use? > Reserved for private use? Is it documented somewhere? > > Should I fear a potential conflict with other devices? I don't think so. This address range is documented - look for assignment of MAC ranges to NIC manufacturers. This range will be documented as reserved for private use or something similar. BTW, recent UMLs changed to using entirely random MACs. Jeff -- Work email - jdike at linux dot intel dot com |
From: Jason L. <lu...@re...> - 2006-11-15 21:39:19
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On Tue, Nov 14, 2006 at 11:37:15AM -0500, Jeff Dike wrote: > This address range is documented - look for assignment of MAC ranges > to NIC manufacturers. This range will be documented as reserved for > private use or something similar. Half of all MAC-48 addresses are "locally administered": those with the second-least-significant bit of the first byte set. > BTW, recent UMLs changed to using entirely random MACs. Not entirely random. random_ether_addr() makes sure the generated address has the "locally administered" bit set, and the broadcast bit cleared: include/linux/etherdevice.h: /** * random_ether_addr - Generate software assigned random Ethernet address * @addr: Pointer to a six-byte array containing the Ethernet address * * Generate a random Ethernet address (MAC) that is not multicast * and has the local assigned bit set. */ static inline void random_ether_addr(u8 *addr) { get_random_bytes (addr, ETH_ALEN); addr [0] &= 0xfe; /* clear multicast bit */ addr [0] |= 0x02; /* set local assignment bit (IEEE802) */ } Jason |
From: Nicolas B. <nic...@ec...> - 2006-11-16 09:48:34
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Jason Lunz wrote: > On Tue, Nov 14, 2006 at 11:37:15AM -0500, Jeff Dike wrote: > >>This address range is documented - look for assignment of MAC ranges >>to NIC manufacturers. This range will be documented as reserved for >>private use or something similar. > > > Half of all MAC-48 addresses are "locally administered": those with the > second-least-significant bit of the first byte set. Uh? Looking at the list of allocated OUI (http://standards.ieee.org/regauth/oui/oui.txt), I see that the following OUI are allocated: 02-07-01 02-1C-7C 02-60-86 02-60-8C 02-70-01 02-70-B0 02-70-B3 02-9D-8E 02-AA-3C 02-BB-01 02-C0-8C 02-CF-1C 02-E6-D3 AA-00-00 AA-00-01 AA-00-02 AA-00-03 AA-00-04 All of them have the second-least-significant bit of the first byte set. If this rule about being locally administered written somewhere? (And, more surprising, there is also 11-00-AA which has the LSB of the first byte set.) Cheers, Nicolas |
From: Jason L. <lu...@re...> - 2006-11-16 17:02:33
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On Thu, Nov 16, 2006 at 10:48:16AM +0100, Nicolas Boullis wrote: > > Half of all MAC-48 addresses are "locally administered": those with the > > second-least-significant bit of the first byte set. > > Uh? > Looking at the list of allocated OUI > (http://standards.ieee.org/regauth/oui/oui.txt), I see that the > following OUI are allocated: yes, I see. 18 of the 9781 assigned OUIs in that listing do have that bit set. Thanks for pointing that out. > All of them have the second-least-significant bit of the first byte set. > If this rule about being locally administered written somewhere? It would seem to contradict http://standards.ieee.org/regauth/groupmac/tutorial.html, though that seems kind of old because it references ISO/IEC 10039 for the definition of MAC addresses, and that's been superceded in 1995 by ISO/IEC 15802-1. I don't have access to either one atm. > (And, more surprising, there is also 11-00-AA which has the LSB of the > first byte set.) indeed, though that allocation is private. So who knows what it's really used for. Jason |