Date: Wed, 7 Jul 2021 19:43:48 -0700 From: Mel Pilgrim <list_freebsd@bluerosetech.com> To: freebsd-lists-5@thismonkey.com Cc: freebsd-questions@freebsd.org Subject: Re: Specifying IPv6 off-link for a subnet Message-ID: <5ea688b3-79b9-8a28-0430-5a4651207ae0@bluerosetech.com> In-Reply-To: <YOMpKMgvV2zs4ZVj@thismonkey.com> References: <YOMpKMgvV2zs4ZVj@thismonkey.com>
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On 2021-07-05 8:45, Scott wrote: > I have manually configured IPv6 on the interfaces: > ifconfig_vmx0_ipv6="inet6 xx::yy prefer_source accept_rtadv -autoconf no_radr" > > The prefix appears in the prefix list as: > # ndp -p > xx::/64 if=vmx0 > flags=LO vltime=infinity, pltime=infinity, expire=Never, ref=1 > No advertising router > > Here's the received RA: > 01:26:48.355186 IP6 (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 64) fe80::1 > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 64 > hop limit 64, Flags [none], pref high, router lifetime 1800s, reachable time 0ms, retrans timer 0ms > source link-address option (1), length 8 (1): 00:00:5e:00:02:02 > mtu option (5), length 8 (1): 9000 > prefix info option (3), length 32 (4): xx::/64, Flags [none], valid > time 3600s, pref. time 60s > > Note that there is no L flag set, so the prefix is off-link. You're misinterpreting what the L flag in a PIO means. If set, the L flag indicates the prefix can be used for on-link determination. But if the L bit is unset, the PIO isn't making any assertion about the prefix being on-link or off-link. More importantly, a host must not use a PIO with L=0 to conclude a prefix is off-link. IOW, it is correct for a host to do nothing when it receives an RA PIO with no flags for an already-configured prefix.
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