strange reverse response

[Rodney J Mertz]

OK can someone help explain what is wrong here. A reverse search without the 
+trace option fails:
-------------------------
# dig -x 217.140.40.10

; <<>> DiG 9.2.4 <<>> -x 217.140.40.10
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 58147
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
----------------------------
But if you add +trace it works properly!


# dig -x 217.140.40.10 +trace

; <<>> DiG 9.2.4 <<>> -x 217.140.40.10 +trace
;; global options:  printcmd
..                       64752   IN      NS      e.root-servers.net.
..                       64752   IN      NS      f.root-servers.net.
..                       64752   IN      NS      g.root-servers.net.
..                       64752   IN      NS      h.root-servers.net.
..                       64752   IN      NS      i.root-servers.net.
..                       64752   IN      NS      j.root-servers.net.
..                       64752   IN      NS      k.root-servers.net.
..                       64752   IN      NS      l.root-servers.net.
..                       64752   IN      NS      m.root-servers.net.
..                       64752   IN      NS      a.root-servers.net.
..                       64752   IN      NS      b.root-servers.net.
..                       64752   IN      NS      c.root-servers.net.
..                       64752   IN      NS      d.root-servers.net.
;; Received 292 bytes from 127.0.0.1#53(127.0.0.1) in 0 ms

217.in-addr.arpa.       86400   IN      NS      SEC1.APNIC.NET.
217.in-addr.arpa.       86400   IN      NS      SEC3.APNIC.NET.
217.in-addr.arpa.       86400   IN      NS      SUNIC.SUNET.SE.
217.in-addr.arpa.       86400   IN      NS      NS-EXT.ISC.ORG.
217.in-addr.arpa.       86400   IN      NS      NS-PRI.RIPE.NET.
217.in-addr.arpa.       86400   IN      NS      TINNIE.ARIN.NET.
217.in-addr.arpa.       86400   IN      NS      NS3.NIC.FR.
;; Received 223 bytes from 192.203.230.10#53(e.root-servers.net) in 73 ms

40.140.217.in-addr.arpa. 172800 IN      NS      ns0.bt.net.
40.140.217.in-addr.arpa. 172800 IN      NS      ns1.bt.net.
40.140.217.in-addr.arpa. 172800 IN      NS      ns2.bt.net.
;; Received 104 bytes from 202.12.29.59#53(SEC1.APNIC.NET) in 219 ms

40.140.217.in-addr.arpa. 300    IN      NS      ns2.syntegra.com.
40.140.217.in-addr.arpa. 300    IN      NS      ns3.syntegra.com.
40.140.217.in-addr.arpa. 300    IN      NS      ns4.syntegra.com.
40.140.217.in-addr.arpa. 300    IN      NS      ns1.syntegra.com.
;; Received 128 bytes from 217.35.209.188#53(ns0.bt.net) in 114 ms

10.40.140.217.in-addr.arpa. 21600 IN    PTR     relay11.mms.eu.btsyntegra.com.
40.140.217.in-addr.arpa. 21600  IN      NS      ns3.syntegra.com.
40.140.217.in-addr.arpa. 21600  IN      NS      ns4.syntegra.com.
40.140.217.in-addr.arpa. 21600  IN      NS      ns1.syntegra.com.
40.140.217.in-addr.arpa. 21600  IN      NS      ns2.syntegra.com.
;; Received 232 bytes from 150.143.80.2#53(ns2.syntegra.com) in 204 ms