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

[Frank Price]

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.

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[John Miller]

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 <[hidden email]> 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

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Frank Price 

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