dhcp gives right IP, but ddns adds wrong one to DNS

Tue Jul 21 21:41:40 UTC 2015

Hi Frank,

So... first thing you might check--is dhcpd configured to hand out leases
for 157.yyy.6.171?  Is there a valid lease for it?  Do you have that IP
configured statically anywhere (since you have update-static-leases on;)?
Do you have supreme.lpdev.foo.com configured statically somewhere?

Less likely: Have you ruled out any sort of caching issues (i.e. are you
running your dig command from the nameserver itself)?  With a 900-second
TTL, it shouldn't be much of an issue, but still....

Likewise, unlikely but curious: if you're in a position to run rndc freeze
lpdev.foo.com, what record(s) actually shows up in the zone file?

John

On Tue, Jul 21, 2015 at 5:19 PM, Frank Price <fprice at lexmark.com> wrote:

> After staring at this for days, I throw myself at the feet of the list and
> beg for enlightenment.
>
> ISC DHCP 4.2.5 on Centos 7, + BIND 9.9.4-RedHat-9.9.4-18.el7_1.1 (Extended
> Support Version)
>
> relevant bits of dhcpd.conf:
>   ddns-update-style interim;
>   ignore client-updates;
>   update-static-leases on;
>   update-conflict-detection false;
>
> I have a server which gets IP from dhcp.  It gets a lease, the IP is set
> properly, it asks for dns updates, and the dns server does ... something
> ... which ends up in it having an A record that is completely wrong (the
> name is right but the IP is wrong).
>
> Even if I freeze my zone and correct everything, after the TTL for the RR,
> something is setting the A RR back to the incorrect IP.  I am really really
> losing it on this one.
>
> Log snippets:
> a)  from the dhcp server.  To me this looks pretty good.  10.xxx.145.177
> is the addr of the server.
>
> Jul 21 14:05:10 dns2 dhcpd: DHCPREQUEST for 10.xxx.145.177 from
> f0:1f:af:ce:d9:34 via 10.xxx.144.3
> Jul 21 14:05:10 dns2 dhcpd: DHCPACK on 10.xxx.145.177 to f0:1f:af:ce:d9:34
> (supreme) via 10.xxx.144.3
> Jul 21 14:05:10 dns2 dhcpd: DHCPREQUEST for 10.xxx.145.177 from
> f0:1f:af:ce:d9:34 (supreme) via 10.xxx.144.2
> Jul 21 14:05:10 dns2 dhcpd: Added new forward map from
> supreme.lpdev.foo.com to 10.xxx.145.177
> Jul 21 14:05:10 dns2 dhcpd: Added reverse map from
> 177.145.xxx.10.in-addr.arpa. to supreme.lpdev.foo.com
> Jul 21 14:05:10 dns2 dhcpd: bind update on 10.xxx.145.177 got ack from
> partner: xid mismatch.
>
> b) from the dns server's updates logging.  Also looks ok to me:
> 21-Jul-2015 14:05:10.479 update: info: client 10.xxx.21.46#56082/key
> lpdev.key: updating zone 'lpdev.foo.com/IN': update unsuccessful:
> supreme.lpdev.foo.com: 'name not in use' prerequisite not satisfied
> (YXDOMAIN)
> 21-Jul-2015 14:05:10.496 update: info: client 10.xxx.21.46#56082/key
> lpdev.key: updating zone 'lpdev.foo.com/IN': update unsuccessful:
> supreme.lpdev.foo.com: 'name not in use' prerequisite not satisfied
> (YXDOMAIN)
> 21-Jul-2015 14:05:10.508 update-security: info: client
> 10.xxx.21.46#56082/key lpdev.key: signer "lpdev.key" approved
> 21-Jul-2015 14:05:10.508 update: info: client 10.xxx.21.46#56082/key
> lpdev.key: updating zone 'lpdev.foo.com/IN': deleting rrset at '
> supreme.lpdev.foo.com' TXT
> 21-Jul-2015 14:05:10.508 update: info: client 10.xxx.21.46#56082/key
> lpdev.key: updating zone 'lpdev.foo.com/IN': adding an RR at '
> supreme.lpdev.foo.com' TXT
> 21-Jul-2015 14:05:10.508 update: info: client 10.xxx.21.46#56082/key
> lpdev.key: updating zone 'lpdev.foo.com/IN': deleting rrset at '
> supreme.lpdev.foo.com' A
> 21-Jul-2015 14:05:10.508 update: info: client 10.xxx.21.46#56082/key
> lpdev.key: updating zone 'lpdev.foo.com/IN': adding an RR at '
> supreme.lpdev.foo.com' A
> 21-Jul-2015 14:05:10.532 update-security: info: client
> 10.xxx.21.46#56082/key lpdev.key: signer "lpdev.key" approved
> 21-Jul-2015 14:05:10.532 update: info: client 10.xxx.21.46#56082/key
> lpdev.key: updating zone '145.xxx.10.in-addr.arpa/IN': deleting rrset at
> '177.145.xxx.10.in-addr.arpa' PTR
> 21-Jul-2015 14:05:10.532 update: info: client 10.xxx.21.46#56082/key
> lpdev.key: updating zone '145.xxx.10.in-addr.arpa/IN': adding an RR at
> '177.145.xxx.10.in-addr.arpa' PTR
>
> c)  here's the lease.  Things still match up.
> lease 10.xxx.145.177 {
>   starts 2 2015/07/21 18:05:10;
>   ends 3 2015/07/22 18:05:10;
>   tstp 4 2015/07/23 06:05:10;
>   tsfp 4 2015/07/23 06:05:10;
>   atsfp 4 2015/07/23 06:05:10;
>   cltt 2 2015/07/21 18:05:10;
>   binding state active;
>   next binding state expired;
>   hardware ethernet f0:1f:af:ce:d9:34;
>   uid "\001\360\037\257\316\3314";
>   set ddns-rev-name = "177.145.xxx.10.in-addr.arpa.";
>   set ddns-txt = "313e29237150b143ecae66d87b9f881997";
>   set ddns-fwd-name = "supreme.lpdev.foo.com";
>   client-hostname "supreme";
> }
>
> Now the kicker:  dig -t any supreme.lpdev.foo.com.  The TXT record is the
> same as the lease, but the IP is 157.yyy.6.171 -- not 10.xxx.145.177.
>
> ; <<>> DiG 9.9.4-RedHat-9.9.4-18.el7_1.1 <<>> -t any supreme.lpdev.foo.com
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 27655
> ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 4, ADDITIONAL: 7
>
> ;; OPT PSEUDOSECTION:
> ; EDNS: version: 0, flags:; udp: 4096
> ;; QUESTION SECTION:
> ;supreme.lpdev.foo.com. IN   ANY
>
> ;; ANSWER SECTION:
> supreme.lpdev.foo.com. 900 IN A      157.yyy.6.171
> supreme.lpdev.foo.com. 900 IN TXT    "319f076f60d81714bcd70f25de57df86b1"
>
> Any clues will be very much appreciated!
>
> -Frank
> --
> Frank Price
>
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>

-- 
John Miller
Systems Engineer
Brandeis University
johnmill at brandeis.edu
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