DDNS update not sent on initial DHCP offer/request/ack
Forman, Jeffrey
lists at jeffreyforman.net
Wed Dec 7 15:33:02 UTC 2016
I've got a fairly standard setup here, ISC dhcpd handing out IPv4 address,
updating a DNS zone handled by BIND with those hostnames. Though it seems
lately (perhaps it's always been this case?) that the first time a new host
comes up and requests an IP from the dhcp server, BIND is not notified of
the new hostname and IP address. I have to reboot the client and then, on
the subsequent request/ack cycle, is DNS updated. So my question is, why do
I have to reboot the clients to get dhcpd to update bind? Is something
misconfigured in my DHCPD to not do the intial update, or is it something
client-side that is needed?
Infrastructure:
- dhcp server os: OpenBSD 6.0 on amd64 ($OPENBSD in the below logs)
- dhcpd version: isc dhcpd 4.3.4
- bind version: isc bind 9.10-4p2
- client OS: CoreOS (though I also run ubuntu and OSX locally as well)
($COREOSCLIENT in the below logs)
>From the DHCPD logs, the initial request:
Dec 7 06:25:49 $OPENBSD dhcpd: DHCPOFFER on 10.10.2.245 to
52:54:00:18:f7:fb via vlan12
Dec 7 06:25:49 $OPENBSD dhcpd: DHCPREQUEST for 10.10.2.245 (10.10.2.1)
from 52:54:00:18:f7:fb via vlan12
Dec 7 06:25:49 $OPENBSD dhcpd: DHCPACK on 10.10.2.245 to 52:54:00:18:f7:fb
via vlan12
I reboot the client, and then:
Dec 7 06:27:59 $OPENBSD dhcpd: DHCPREQUEST for 10.10.2.245 (10.10.2.1)
from 52:54:00:18:f7:fb via vlan12
Dec 7 06:27:59 $OPENBSD dhcpd: DHCPACK on 10.10.2.245 to 52:54:00:18:f7:fb
(coreE3) via vlan12
07-Dec-2016 06:27:59.177 update-security: info: client 10.10.2.1#28804/key
$TSIG-KEY: signer "$TSIG-KEY" approved
07-Dec-2016 06:27:59.177 update: info: client 10.10.2.1#28804/key
$TSIG-KEY: updating zone 'dns.zone.net/IN': adding an RR at '$COREOSCLIENT'
A 10.10.2.245
07-Dec-2016 06:27:59.177 update: info: client 10.10.2.1#28804/key
$TSIG-KEY: updating zone 'dns.zone.net/IN': adding an RR at '$COREOSCLIENT'
TXT "31b0331ba3cfc488d24fbfc87f9e127924"
Dec 7 06:27:59 $OPENBSD dhcpd: Added new forward map from $COREOSCLIENT to
10.10.2.245
07-Dec-2016 06:27:59.182 update-security: info: client 10.10.2.1#28804/key
$TSIG-KEY: signer "$TSIG-KEY" approved
07-Dec-2016 06:27:59.182 update: info: client 10.10.2.1#28804/key
$TSIG-KEY: updating zone '2.10.10.in-addr.arpa/IN': deleting rrset at
'245.2.10.10.in-addr.arpa' PTR
07-Dec-2016 06:27:59.182 update: info: client 10.10.2.1#28804/key
$TSIG-KEY: updating zone '2.10.10.in-addr.arpa/IN': adding an RR at
'245.2.10.10.in-addr.arpa' PTR $COREOSCLIENT.
relevant dhcpd config:
ddns-updates on;
ddns-update-style interim;
update-optimization off;
subnet 10.10.2.0 netmask 255.255.255.0 {
range 10.10.2.200 10.10.2.250;
option routers 10.10.2.1;
option domain-name-servers 10.10.2.1;
zone dns.zone.net {
primary 10.10.2.1;
key "$TSIG-KEY";
}
zone 2.10.10.in-addr.arpa {
primary 10.10.2.1;
key "$TSIG-KEY";
}
}
What am I missing here? Why does it require a restart of the client to get
the dns entry added?
Thanks,
Jeff
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