Re: IPv6 neighbor flaps for ISP router are occurring frequently

Apologies for lack of important context, the below discusses a FreeBSD
14.1 amd64 system.

Thank you.

> On Sep 16, 2024, at 16:05, Chris Ross <cross+freebsd@distal.com> wrote:
> 
> Hello.  Following the earlier thread "DHCPv6 IA_PD - how-to” I have been
> bringing up a new gateway router for my network.  With Roy’s help, I
> have IPv6 working as expected, but I am seeing something that I suspect
> is unusual.  Roy doesn’t think it’s specific to dhcpcd, as it is caused
> by routing changes that dhcpcd is merely reacting to.
> 
> While dhcpcd is running, it repeatedly logs the following to daemon.log:
> 
> Sep 16 15:55:53 logrus dhcpcd[50070]: vlan0: fe80::3e8a:b0ff:fe3e:4dce is unreachable
> Sep 16 15:55:54 logrus dhcpcd[50070]: vlan0: fe80::3e8a:b0ff:fe3e:4dce is reachable again
> Sep 16 15:55:54 logrus dhcpcd[50070]: vlan0: soliciting an IPv6 router
> Sep 16 15:56:25 logrus dhcpcd[50070]: vlan0: fe80::3e8a:b0ff:fe3e:4dce is unreachable
> Sep 16 15:56:25 logrus dhcpcd[50070]: vlan0: fe80::3e8a:b0ff:fe3e:4dce is reachable again
> Sep 16 15:56:25 logrus dhcpcd[50070]: vlan0: soliciting an IPv6 router
> Sep 16 15:56:57 logrus dhcpcd[50070]: vlan0: fe80::3e8a:b0ff:fe3e:4dce is unreachable
> Sep 16 15:56:58 logrus dhcpcd[50070]: vlan0: soliciting an IPv6 router
> Sep 16 15:56:58 logrus dhcpcd[50070]: vlan0: Router Advertisement from fe80::3e8a:b0ff:fe3e:4dce
> Sep 16 15:57:32 logrus dhcpcd[50070]: vlan0: fe80::3e8a:b0ff:fe3e:4dce is unreachable
> Sep 16 15:57:32 logrus dhcpcd[50070]: vlan0: soliciting an IPv6 router
> Sep 16 15:57:32 logrus dhcpcd[50070]: vlan0: Router Advertisement from fe80::3e8a:b0ff:fe3e:4dce
> 
> During this same time frame, “route monitor” shows:
> 
> 15:55:53.573 PID    0 delete neigh fe80::3e8a:b0ff:fe3e:4dce%vlan0 state PROBE lladdr 3c:8a:b0:3e:4d:ce iface vlan0  15:55:54.002 PID    0 add/repl neigh fe80::3e8a:b0ff:fe3e:4dce%vlan0 state REACHABLE lladdr 3c:8a:b0:3e:4d:ce iface vlan0  15:56:25.148 PID    0 delete neigh fe80::3e8a:b0ff:fe3e:4dce%vlan0 state PROBE lladdr 3c:8a:b0:3e:4d:ce iface vlan0  15:56:25.212 PID    0 add/repl neigh fe80::3e8a:b0ff:fe3e:4dce%vlan0 state REACHABLE lladdr 3c:8a:b0:3e:4d:ce iface vlan0  15:56:57.406 PID    0 delete neigh fe80::3e8a:b0ff:fe3e:4dce%vlan0 state PROBE lladdr 3c:8a:b0:3e:4d:ce iface vlan0  15:56:58.967 PID    0 add/repl neigh fe80::3e8a:b0ff:fe3e:4dce%vlan0 state REACHABLE lladdr 3c:8a:b0:3e:4d:ce iface vlan0  15:57:32.325 PID    0 delete neigh fe80::3e8a:b0ff:fe3e:4dce%vlan0 state PROBE lladdr 3c:8a:b0:3e:4d:ce iface vlan0  15:57:34.143 PID    0 add/repl neigh fe80::3e8a:b0ff:fe3e:4dce%vlan0 state REACHABLE lladdr 3c:8a:b0:3e:4d:ce iface vlan0  
> 
> My concern is that this is sending RS’s to my provider far too often.
> Can anyone advise if this is normal, and assuming not, what might
> be wrong?
> 
> Trimmed dhcpcd.conf is:
> 
> duid
> persistent
> vendorclassid
> option classless_static_routes
> option rapid_commit
> require dhcp_server_identifier
> slaac private
> noipv6rs
> noipv4
> noipv4ll
> allowinterfaces vlan0
> interface vlan0
>  ipv6only
>  ipv6rs
>  ipv6ra_autoconf
>  ia_pd 0/::/56 intnet1/42 intnet2/56
> 
> Thanks.
> 
>                        - Chris
>