Re: IPv6 neighbor flaps for ISP router are occurring frequently

From: Karl Denninger <karl_at_denninger.net>
Date: Mon, 16 Sep 2024 21:55:52 UTC
What is the revision on the kernel (rev and/or build date)?

I THINK the only difference between you and I that is material is that 
I'm running dhcp6c because dhcpcd, at least check, has some trouble 
getting an allocation on cold boot (but does if restarted), on which 
I've communicated with Roy, and I haven't seen anything new pop up on 
the dhcpcd port yet thus haven't tried it again in the ~4 weeks.

I'm /not /seeing it here but I might not have /all /the patches you're 
referring to on the gateway.  If I'm not its easily enough rolled 
forward here so I do.

I have a non-routing machine that is very current (rebuilt after the 
recent zfs patch set hit) on stable/14 and it is not seeing that -- but 
it is not a router, it is an end-node running rtsold and gets its IPv6 
address via SLACC from the router.

On 9/16/2024 17:45, Chris Ross wrote:
> 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
>>
>
>
-- 
Karl Denninger
karl@denninger.net
/The Market Ticker/
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