[SOLVED] IPv6 Log Entry Question (dhcp6c)

[ProximusAl]

Hi All,

Quick question for any experts out there.

I get IPv6 over PPPoE and only set the following on the WAN interface:

IPv6 Configuration Type: DHCPv6
Prefix Delegation Size: 48

Everything else is unticked, including "Send prefix hint" and "Request prefix only"

IPv6 actually works perfectly well, with a /64 on the WAN, and a chunk of my /48 on the LAN(/64) but I get a lot of these entries in the log.

2026-03-20T11:03:54    Notice    dhcp6c    advertise contains no address/prefix
2026-03-20T11:03:54    Notice    dhcp6c    Sending Solicit on pppoe0

Is there anything I can do to suppress "advertise contains no address/prefix" or is this normal?

Thanks...

[franco]

It's somewhat important because whatever dhcp6c tried to do failed. If you want to look closer use debug logging for IPv6. If not please ignore.


Cheers,
Franco

[ProximusAl]

Thanks Franco,

Seems to be on the hour-ish

2026-03-20T12:05:16Noticedhcp6cadvertise contains no address/prefix
2026-03-20T12:05:16Noticedhcp6cSending Solicit on pppoe0
2026-03-20T11:03:54Noticedhcp6cadvertise contains no address/prefix
2026-03-20T11:03:54Noticedhcp6cSending Solicit on pppoe0
2026-03-20T10:03:11Noticedhcp6cadvertise contains no address/prefix
2026-03-20T10:03:11Noticedhcp6cSending Solicit on pppoe0
2026-03-20T09:05:49Noticedhcp6cadvertise contains no address/prefix
2026-03-20T09:05:49Noticedhcp6cSending Solicit on pppoe0
2026-03-20T08:08:39Noticedhcp6cadvertise contains no address/prefix
2026-03-20T08:08:39Noticedhcp6cSending Solicit on pppoe0
2026-03-20T07:09:46Noticedhcp6cadvertise contains no address/prefix
2026-03-20T07:09:45Noticedhcp6cSending Solicit on pppoe0

How do I enable IPv6 debug?

[franco]

Interfaces: Settings: Debug logging

Needs a reboot.


Cheers,
Franco

[ProximusAl]

I've Xed out some bits:

2026-03-20T13:50:26Noticedhcp6cadvertise contains no address/prefix
2026-03-20T13:50:26Noticedhcp6cserver ID: 00:XX:00:00:XX:XX:XX:XX:XX:37:66:3a:66:38:3a:37:34:3a:62:63:XX:XX:XX:00:00:00, pref=-1
2026-03-20T13:50:26Noticedhcp6cstatus code: no addresses
2026-03-20T13:50:26Noticedhcp6cget DHCP option status code, len 43
2026-03-20T13:50:26Noticedhcp6cIA_NA: ID=5, T1=0, T2=0
2026-03-20T13:50:26Noticedhcp6cget DHCP option identity association, len 59
2026-03-20T13:50:26Noticedhcp6cDUID: 00:XX:00:00:XX:XX:XX:XX:3a:37:66:3a:66:38:3a:37:34:3a:62:63:XX:XX:XX:00:00:00
2026-03-20T13:50:26Noticedhcp6cget DHCP option server ID, len 26
2026-03-20T13:50:26Noticedhcp6cDUID: 00:0X:00:0X:XX:dc:XX:1d:f4:90:XX:01:cb:XX
2026-03-20T13:50:26Noticedhcp6cget DHCP option client ID, len 14
2026-03-20T13:50:26Noticedhcp6creceive advertise from fe80::200:ff:fe00:0%pppoe0 on pppoe0
2026-03-20T13:50:26Noticedhcp6creset a timer on pppoe0, state=SOLICIT, timeo=5, retrans=35593
2026-03-20T13:50:26Noticedhcp6csend solicit to ff02::1:2%pppoe0
2026-03-20T13:50:26Noticedhcp6cset elapsed time (len 2)
2026-03-20T13:50:26Noticedhcp6cset identity association
2026-03-20T13:50:26Noticedhcp6cset client ID (len 14)
2026-03-20T13:50:26Noticedhcp6cSending Solicit on pppoe0

[ProximusAl]

If I "Request Prefix Only" the problem goes away......

So that is what I shall do, even though the ISP gives me a /64 for WAN.

This is ZEN UK.

EDIT: Looks like ZEN give the WAN IP via SLAAC, not IA_NA, and thats where the issue was.

[franco]

So you don't get a NA (non-temporary address) even if you request it... prefix only avoids requesting it. The outcome is the same minus the error in the log.


Cheers,
Franco

[ProximusAl]

I do get a non temporary address yes, but it seems to come via SLAAC. (If I untick request prefix only)

So requesting a prefix only gives fe80::1%pppoe0/64 on the WAN, unticking Request Prefix only gives an address in my ND, e.g. 2a02:X0XX:XX01:XX6a::1/64, but then I get the entries in the log no address/prefix.

I think dhcp6c is trying to get the WAN IPv6 via DHCPv6 and thats why it throws no addresses.

The PD comes via DHCPv6, and that always works.

What is very interesting though, is even though I request prefix only, under Interfaces/Overview, I do still see the above ND address, but not on the dashboard interfaces widget, just fe80::1%pppoe0/64

Odd....

It's not a major issue for me as *both* options work, I was just interested in why the log was displaying those messages.

Keep up the good work Franco :)

[franco]

The NA is /128. SLAAC is /64 and should always be there (because SLAAC is also required for the routing which DHCPv6 doesn't do at all).

The fact that you don't get an error on the first try is that it requests the PD and the NA in one request and that is fulfilled by the PD. Once it retries the NA request on its own the error starts happening.


Cheers,
Franco

[ProximusAl]

Now that makes a lot more sense :)

In which case, I change my answer to I never get a /128 :)

Perhaps a poorly setup at the ZEN ISP end then....

For now, because I am a *clean log* man, I just request a PD only.  It works for me.

[franco]

Ok, nice.  This setup can be perfectly normal.  No need to throw shade at Zen for that (at least this time).  :)


Cheers,
Franco