Internal DNS doesn’t work with CNAME

amazon-elbamazon-web-servicesdomain-name-systeminternal-dns

I have an internal DNS setup setup in my AWS VPC network, I just created an internal load balancer and added a CNAME record to this load balancer, but it's not working.

DNS CNAME entry:

db1     IN      CNAME   internal-DB1-1579653487.us-east-1.elb.amazonaws.com.

nslookup looks good:

epf-mac:~ erico$ nslookup -q=CNAME db1
Server:     10.0.200.4
Address:    10.0.200.4#53

db1.example.com canonical name = internal-DB1-1579653487.us-east-1.elb.amazonaws.com.

Load balancer hostname points to 2 IPs (Load Balancer working in two subnets).

epf-mac:~ erico$ nslookup internal-DB1-1579653487.us-east-1.elb.amazonaws.com.
Server:     10.0.200.4
Address:    10.0.200.4#53

Non-authoritative answer:
Name:   internal-DB1-1579653487.us-east-1.elb.amazonaws.com
Address: 10.0.211.228
Name:   internal-DB1-1579653487.us-east-1.elb.amazonaws.com
Address: 10.0.200.65

But actual name doesn't work:

epf-mac:~ erico$ ping db1
ping: cannot resolve db1: Unknown host
epf-mac:~ erico$ dig db1

; <<>> DiG 9.8.3-P1 <<>> db1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 39452
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;db1.               IN  A

;; AUTHORITY SECTION:
.           9456    IN  SOA a.root-servers.net. nstld.verisign-grs.com. 2014100901 1800 900 604800 86400

;; Query time: 165 msec
;; SERVER: 10.0.200.4#53(10.0.200.4)
;; WHEN: Thu Oct  9 21:10:30 2014
;; MSG SIZE  rcvd: 96

—– EDIT (FIXED) —–

I don't know exactly what it was, but the entry started working without make any additional changes, some DNS caching probably.

Best Answer

It wasn't any sort of negative caching. Take another look at the actual query that was performed:

;; QUESTION SECTION:
;db1.               IN  A

The trailing dot means that the query was for a FQDN of db. (note the trailing dot), and your search suffix of example.com was not automatically suffixed. The dig command does not automatically append the search suffix specified in /etc/resolv.conf. From the manpage:

  +[no]search
      Use [do not use] the search list defined by the searchlist or domain
      directive in resolv.conf (if any). The search list is not used by
      default.
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