BIND server; dig vs dig +trace on failing lookup.

[Gregory Sloop]

Let me take a swing at it. If I'm wrong, someone correct me.

1) dig the name servers for the 1st level domain. (In this case, it's a .com.)
# dig +short com. NS
c.gtld-servers.net.
f.gtld-servers.net.
j.gtld-servers.net.
l.gtld-servers.net.
k.gtld-servers.net.
d.gtld-servers.net.
g.gtld-servers.net.
i.gtld-servers.net.
a.gtld-servers.net.
e.gtld-servers.net.
m.gtld-servers.net.
b.gtld-servers.net.
h.gtld-servers.net.
---

2) How, ask one of those name servers for the NS for the target domain. (cistus.com. in this case.)

# dig +norec @i.gtld-servers.net. cistus.com. NS

; <<>> DiG 9.11.3-1ubuntu1.14-Ubuntu <<>> +norec @i.gtld-servers.net. cistus.com. NS
; (2 servers found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 49843
;; flags: qr; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 3

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;cistus.com.                    IN      NS

;; AUTHORITY SECTION:
cistus.com.             172800  IN      NS      srvns.pacifier.com.
cistus.com.             172800  IN      NS      webns.pacifier.com.

;; ADDITIONAL SECTION:
srvns.pacifier.com.     172800  IN      A       216.65.128.5
webns.pacifier.com.     172800  IN      A       216.65.128.1

---

3) Finally, query the records in the additional section to see if they match the glue records.

# dig srvns.pacifier.com.

; <<>> DiG 9.11.3-1ubuntu1.14-Ubuntu <<>> srvns.pacifier.com.
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 17445
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: d16ea0cbd520a81cea1154c1603ef7e13d586e8adc0e75f3 (good)
;; QUESTION SECTION:
;srvns.pacifier.com.            IN      A

;; ANSWER SECTION:
srvns.pacifier.com.     85728   IN      A       64.255.237.241

;; AUTHORITY SECTION:
pacifier.com.           172126  IN      NS      ns2.iinet.com.
pacifier.com.           172126  IN      NS      ns4.iinet.com.
pacifier.com.           172126  IN      NS      ns1.iinet.com.
pacifier.com.           172126  IN      NS      ns3.iinet.com.
----

(glue) srvns.pacifier.com.     172800  IN      A       216.65.128.5
vs
(regular lookup) srvns.pacifier.com.     85728   IN      A       64.255.237.241

And they don't - so we know the glue is stale.


Is that right? :)

-Greg


Would you mind showing me how you got there?
[The answer is fab, obviously. But give a man a fish...and all that. :) ]

-Greg



MA> The COM servers have stale glue

MA> srvns.pacifier.com.     172800  IN      A       216.65.128.5
MA> webns.pacifier.com.     172800  IN      A       216.65.128.1

MA> vs

MA> srvns.pacifier.com.     86400   IN      A       64.255.237.241
MA> webns.pacifier.com.     86400   IN      A       64.255.237.240

MA> The later set of servers are what you query when you run dig +trace.
MA> If you prime the cache the plain lookup should work.  Report the out
MA> of date glue to the zone administrator.

MA> Mark

>> On 3 Mar 2021, at 13:06, Gregory Sloop <gregs at sloop.net> wrote:

>> I've got a case, (and I see several other similar reports) where BIND is failing to find an A record for a domain.
>> Yet a dig +trace does.

>> (I'm doing the dig on the BIND server. It's set to be a root resolving server, not a forwarder.)

>> As I understand this, +trace will also involve resolve.conf options. And in this case, I've got Google DNS as one of the resolve.conf entries.
>> So, I can see how +trace would deliver different results than simply dig-ing - provided that +trace does involve resolve.conf.

>> Here's a plain dig, using the BIND server itself - from the console.
>> ---
>> dig cistus.com @10.8.20.5

>> ; <<>> DiG 9.11.3-1ubuntu1.14-Ubuntu <<>> cistus.com @10.8.20.5
>> ;; global options: +cmd
>> ;; Got answer:
>> ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 61786
>> ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

>> ;; OPT PSEUDOSECTION:
>> ; EDNS: version: 0, flags:; udp: 4096
>> ; COOKIE: 13ec0c9b10770ea12426539e603957900a997f7258962cce (good)
>> ;; QUESTION SECTION:
>> ;cistus.com.                    IN      A

>> ;; Query time: 0 msec
>> ;; SERVER: 10.8.20.5#53(10.8.20.5)
>> ;; WHEN: Fri Feb 26 12:18:24 PST 2021
>> ;; MSG SIZE  rcvd: 67

>> ---

>> I could post the dig +trace, if it adds any information, but I suspect it doesn't.

>> So, what methods or steps might I take to figure out why the above lookup/dig fails?
>> [I intended +trace to do that, but since it's not doing the same thing a plain dig does, it's not very useful as a diagnostic tool.]

>> I've done some searching to see how to accomplish this, but it's a difficult question to frame without a ton of worthless hits.
>> So, can someone point me at a good source for a how-to/walk-through? A previous list posting?

>> Again, the question is; what methods or steps (best practices) might I take to figure out why the above lookup/dig fails?

>> TIA
>> -Greg
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