Send dhcp-users mailing list submissions to
dhcp-users@lists.isc.org
To subscribe or unsubscribe via the World Wide Web, visit
https://lists.isc.org/mailman/listinfo/dhcp-users
or, via email, send a message with subject or body 'help' to
dhcp-users-requ...@lists.isc.org
You can reach the person managing the list at
dhcp-users-ow...@lists.isc.org
When replying, please edit your Subject line so it is more specific
than "Re: Contents of dhcp-users digest..."
Today's Topics:
1. Unexpected DDNS name removal. (Gregory Sloop)
----------------------------------------------------------------------
Message: 1
Date: Fri, 24 Jun 2022 19:23:10 -0700
From: Gregory Sloop <gr...@sloop.net>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Unexpected DDNS name removal.
Message-ID: <15010291528.20220624192...@sloop.net>
Content-Type: text/plain; charset="utf-8"
I've got a pretty weird situation here.
I have some Canon MFC's (MF1643i, if it matters)
We have a half a dozen or so.
They have a pretty odd relationship with the DHCP servers.
They'll get an IP fine, and stay up for days, but then suddenly they'll simply
fail to renew the IP and get a 169 address. There's a setting in the network
control panel to turn off "Auto IP" which appears to be a "feature" that might
do this.
I've turned it off on a few, but I can't tell if that's fixed anything - since
it only happens occasionally.
?
But that's not the real question. I only mention this because it might have
bearing on another issue.
Along with the DHCP reservation (via a class statement that puts these printers
in a specific pool/address-space) - I also have dhcpd creating DDNS records for
them. We point print clients at the FQDN of the printer.?
(I won't get into why we like having the printers on DHCP, but there are some
nice advantages.)
However, what I'm seeing now is that the printer will renew the lease at the
50% mark, and in the logs I see it request and ACK the lease renewal, but then
there's an immediate DDNS forward map removal.
Here's some lightly sanitized logs. (The logs are from the syslog server, so
you're seeing logs from both DHCP servers, not just one; we run a
failover/balance DHCP pair.)
You can see the "start" of one of these events. The forward map is removed.?
(And obviously, if we're printing to this printer with the FQDN this because a
big problem.)
?
I have a monitor on this printer currently, so I notice it went down, and can't
do name resolution.
It's still got an IP and I can still talk to it via the IP.
So, I simply force the printer to re-start.
AFAICT, DHCP still thinks it's got an active lease. (Born out my the
reuse_lease message.)
It goes about doing a discovery gets an offer ACKS the lease, and re-creates
the forward map for my FQDN.
The lease is 8H, BTW.
So, at 4H it renews, but then for some reason DHCPD removes the forward again.
(Though DHCP shouldn't remove the forward until the client explicitly releases
the lease, or fails to renew in 8H.)
Jun 24 13:46:27 my-dns-dhcp-2 dhcpd[721]: Removed forward map from
my-scanner-scan.mydom.local to 10.8.28.83
Jun 24 13:57:56 my-dns-dhcp-1 dhcpd[13147]: DHCPDISCOVER from 74:bf:c0:11:22:33
(my-scanner-scan) via 10.8.28.1: load balance to peer dhcp-failover
Jun 24 13:57:56 my-dns-dhcp-2 dhcpd[721]: reuse_lease: lease age 689 (secs)
under 25% threshold, reply with unaltered, existing lease for 10.8.28.83
Jun 24 13:57:56 my-dns-dhcp-2 dhcpd[721]: DHCPDISCOVER from 74:bf:c0:11:22:33
via 10.8.28.1
Jun 24 13:57:57 my-dns-dhcp-2 dhcpd[721]: DHCPOFFER on 10.8.28.83 to
74:bf:c0:11:22:33 via 10.8.28.1
Jun 24 13:57:57 my-dns-dhcp-1 dhcpd[13147]: DHCPREQUEST for 10.8.28.83
(10.8.20.6) from 74:bf:c0:11:22:33 (my-scanner-scan) via 10.8.28.1
Jun 24 13:57:57 my-dns-dhcp-1 dhcpd[13147]: DHCPACK on 10.8.28.83 to
74:bf:c0:11:22:33 (my-scanner-scan) via 10.8.28.1
Jun 24 13:57:57 my-dns-dhcp-2 dhcpd[721]: DHCPREQUEST for 10.8.28.83
(10.8.20.6) from 74:bf:c0:11:22:33 via 10.8.28.1
Jun 24 13:57:57 my-dns-dhcp-2 dhcpd[721]: DHCPACK on 10.8.28.83 to
74:bf:c0:11:22:33 (my-scanner-scan) via 10.8.28.1
Jun 24 13:57:57 my-dns-dhcp-2 dhcpd[721]: bind update on 10.8.28.83 from
dhcp-failover rejected: incoming update is less critical than outgoing update
Jun 24 13:57:57 my-dns-dhcp-1 dhcpd[13147]: Added new forward map from
my-scanner-scan.mydom.local to 10.8.28.83
Jun 24 13:57:57 my-dns-dhcp-2 dhcpd[721]: Added new forward map from
my-scanner-scan.mydom.local to 10.8.28.83
Jun 24 17:57:57 my-dns-dhcp-2 dhcpd[721]: DHCPREQUEST for 10.8.28.83 from
74:bf:c0:11:22:33 (my-scanner-scan) via eth1
Jun 24 17:57:57 my-dns-dhcp-2 dhcpd[721]: DHCPACK on 10.8.28.83 to
74:bf:c0:11:22:33 via eth1
Jun 24 17:57:57 my-dns-dhcp-2 dhcpd[721]: Removed forward map from
my-scanner-scan.mydom.local to 10.8.28.83
---
Since this isn't happening for any other clients in the network, and no other
make/model of printers, I assume the printer must be doing something that
provokes it.?But I have no idea how to stop it, what's wrong etc.
And it doesn't happen all the time for all these Canon printers. Just some,
some of the time.
Gak!
Yeah, probably packet caps are the best option, but when it's sporadic, that's
kind of hard to do.
I guess I'm here asking "Has anyone seen anything like this, before? And if so,
what kinds of things might be the culprit."
[Hey, at least it accepts a lease < 1Y, eh Simon!?! :) ]
?
TIA
-Greg
?
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<https://lists.isc.org/pipermail/dhcp-users/attachments/20220624/ac31f6f5/attachment-0001.htm>
------------------------------
Subject: Digest Footer
_______________________________________________
ISC funds the development of this software with paid support subscriptions.
Contact us at https://www.isc.org/contact/ for more information.
dhcp-users mailing list
dhcp-users@lists.isc.org
https://lists.isc.org/mailman/listinfo/dhcp-users
------------------------------
End of dhcp-users Digest, Vol 164, Issue 31
*******************************************
