Date: Fri, 29 Jun 2001 11:00:18 +0900 From: JINMEI Tatuya / =?ISO-2022-JP?B?GyRCP0BMQEMjOkgbKEI=?= <jinmei@isl.rdc.toshiba.co.jp> To: freebsd-net@FreeBSD.ORG Cc: oberman@es.net Subject: Re: Odd IPv6 behavior when not connected to IPv6 net Message-ID: <y7v1yo4jb9p.wl@condor2.jinmei.org> In-Reply-To: <20010629.061228.59498657.ume@mahoroba.org> References: <20010629.041242.55441386.ume@mahoroba.org> <200106281919.f5SJJ4c23535@ptavv.es.net> <20010629.061228.59498657.ume@mahoroba.org>
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>>>>> On Fri, 29 Jun 2001 06:12:28 +0900 (JST), >>>>> Hajimu UMEMOTO <ume@mahoroba.org> said: oberman> I agree, but I have made no deliberate changes. I just install FreeBSD oberman> with ipv6_enable="YES" in rc.config. oberman> Internet6: oberman> Destination Gateway Flags Netif Expire oberman> :: localhost UGRSc lo0 => oberman> default fe80::1%lo0 Uc lo0 > Why are you set ipv6_enable to YES while you are not using IPv6? :-) > I just could reproduce your problem. When no RA is available, default > route is wrongly installed by `ndp -I'. > Please set ipv6_default_interface to NO in your rc.conf. Current its > default setting is meaningless in most cases and it is harmful. I'll > change default of ipv6_default_interface to NO. Please let me explain the rationale. The notion of "ipv6_default_interface" is introduced mainly for conformance to the following part of RFC 2461: Next-hop determination for a given unicast destination operates as follows. The sender performs a longest prefix match against the Prefix List to determine whether the packet's destination is on- or off-link. If the destination is on-link, the next-hop address is the same as the packet's destination address. Otherwise, the sender selects a router from the Default Router List (following the rules described in Section 6.3.6). If the Default Router List is empty, <--- the sender assumes that the destination is on-link. <--- That is, if we do not have any default router (hear from RA), we should regard all IPv6 prefixes as on-link. To implement this trick, we use the "default interface", and install the default route as an interface direct route to the interface. However, as shown in this thread, this feature is basically meaningless, and even harmful, especially when using IPv4 as well. Thus, for the moment, I agree that we should turn the default interface off by default. For a longer term solution, we might have to consider a better source address selection algorithm, e.g. described in draft-ietf-ipngwg-default-addr-select-04.txt. Then IPv4 would be preferred in this case. JINMEI, Tatuya Communication Platform Lab. Corporate R&D Center, Toshiba Corp. jinmei@isl.rdc.toshiba.co.jp To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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