On 8/20/2008 at 11:57 AM, Iljitsch van Beijnum <iljitsch@muada.com> wrote: On 20 aug 2008, at 20:34, Crist Clark wrote:
On a "true" P-to-P link, there is no netmask, no? A netmask is a concept that applies to broadcast media, like Ethernet. Even if you only have two hosts on an Ethernet link, it's not really P-to-P in the strict sense.
An interface needs a prefix length (subnet mask for those of us stuck
in the '90s) so the system knows which addresses are directly connected through the interface in question. Whether the link is point- to-point, broadcast or NBMA doesn't matter for that purpose.
No, that's my point. On a true point-to-point link, there is only one other address on the link. That's what point-to-point means. And no, that does not really mean there is an implied /32 (for IPv4) or /128 (for IPv6) on the link since that would tell the system its the only address on the link. For example, on the IPv4 ends gif(4) tunnel in my previous message, gif0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> metric 0 mtu 1280 tunnel inet 24.6.175.101 --> 72.52.104.74 inet6 fe80::200:24ff:feca:91b4%gif0 prefixlen 64 scopeid 0x7 inet6 2001:470:1f04:2fc::2 --> 2001:470:1f04:2fc::1 prefixlen 128 A netmask doesn't make sense. They're not on the same LAN since there is no LAN on a point-to-point tunnel. (The most specific mask those two share is 0x8000000.) As for the IPv6 portion, the two endpoints happen to be adjacent, they look like they are "on the same network," but there is no reason that has to be in the general case just like the IPv4 case. There is no LAN. It's point-to-point. It could be, 2001:470:8045:0:2b0:d0ff:fe2c:982d --> 2001:470:1f04:2fc::1 (That only happen share the /16 belonging to the ISP, not even on the same /64) and everything would be fine. Right? Or is something different about IPv6? I'm wondering if all of this confusion is about people calling an Ethernet, or other broadcast media, link with only two interfaces on it point-to-point. It's not. B¼information contained in this e-mail message is confidential, intended only for the use of the individual or entity named above. If the reader of this e-mail is not the intended recipient, or the employee or agent responsible to deliver it to the intended recipient, you are hereby notified that any review, dissemination, distribution or copying of this communication is strictly prohibited. If you have received this e-mail in error, please contact postmaster@globalstar.com