a few questions about BIND (MX and Reverse)

romeo_tango · 10-14-2008, 11:58 PM

hi, i just setup named in a box. This box #1 is acting as the DNS server for my LAN. The domain I added in the box #1 is able to be resolved by the LAN which the DNS server is pointing to it. So, I called that named is properly working rite now.

What confuses me are :

1). The MX Records. I use this mxtoolbox [dot] com/index.aspx page to check my MX. Sometimes it shows a valid records like this :

Preference Host Name IP Address TTL
30 a.domain.com 1.2.3.4 3600

but if i refreshed the page, sometimes it will shows :

Preference Host Name IP Address TTL
10 a.domain.com.domain.com 1.2.3.4 3600

Why is that happening? If I looked it up a few times, it will shows correct values again.. Did I misconfigured something in named conf or its just the mxtoolbox.com page that causing that?

This is how MX configured in my zone file :

Code:

$TTL    3600
$ORIGIN domain.com.
@       IN      SOA     a.domain.com. admin.domain.com. (
                                        2008101009      ; serial
                                        3H              ; refresh
                                        15M             ; retry
                                        1W              ; expiry
                                        1D )            ; minimum

                IN NS           ns1.domain.com.
                IN MX   30      ex.domain.com.
                
                IN A            1.2.3.4

mail             IN A            1.2.3.4

is there anything incorrect ?

2). Do I need to add reverse zone? sorry but I still not understand about what this reverse zone for.

WorldIsNotFair · 10-15-2008, 12:16 AM

1. have you tried to query your mx record from client with host -t mx [host] or dig -t mx [host] ,
since you only have 1 mx record, try to change 30 to 10.

2. reverse zone is purposed to resolve ip to hostname.

hope help.

romeo_tango · 10-15-2008, 01:15 AM

Quote:

Originally Posted by WorldIsNotFair

1. have you tried to query your mx record from client with host -t mx [host] or dig -t mx [host] ,
since you only have 1 mx record, try to change 30 to 10.

hmm, there are 2 conditions here :
- If I set the DNS Server is the box #1 which I configured, the dig will return okay like this

Code:

# dig -t mx domain.com

; <<>> DiG 9.2.4 <<>> -t mx domain.com
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 49335
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 3, ADDITIONAL: 6

;; QUESTION SECTION:
;domain.com.                  IN      MX

;; ANSWER SECTION:
domain.com.           3600    IN      MX      30 ex.domain.com.

;; AUTHORITY SECTION:
domain.com.           3600    IN      NS      ns1.domain.com

;; ADDITIONAL SECTION:
ns1.domain.com.  3600    IN      A       1.2.3.4

;; Query time: 76 msec
;; SERVER: 1.2.3.4#53(1.2.3.4)
;; WHEN: Wed Oct 15 13:03:26 2008
;; MSG SIZE  rcvd: 260

- if I use other public DNS, the dig will return :

Code:

# dig -t mx domain.com

; <<>> DiG 9.2.4 <<>> -t mx domain.com
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 44551
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 3, ADDITIONAL: 3

;; QUESTION SECTION:
;domain.com.                  IN      MX

;; ANSWER SECTION:
domain.com.           3592    IN      MX      10 ex.domain.com.domain.com.

;; AUTHORITY SECTION:
domain.com.           3600    IN      NS      ns1.domain.com

;; ADDITIONAL SECTION:
ns1.domain.com.  3600    IN      A       1.2.3.4

;; Query time: 23 msec
;; SERVER: 202.x.x.x#53(202.x.x.x)
;; WHEN: Wed Oct 15 13:06:46 2008
;; MSG SIZE  rcvd: 204

For an additional information, this is a migrated DNS from a Win2K Box. The Win2K Box is now already offline.

Quote:

2. reverse zone is purposed to resolve ip to hostname.

sorry, i mean, do I need to add this zone ?

Thanks for your help Sir.

romeo_tango · 10-15-2008, 01:26 AM

I also try from another ISP's DNS and this what I've got :

Code:

# host -t mx domain.com
domain.com mail is handled by 30 ex.domain.com.

# host -t mx domain.com
domain.com mail is handled by 10 ex.domain.com.domain.com.

# host -t mx domain.com
domain.com mail is handled by 30 ex.domain.com.

# host -t mx domain.com
domain.com mail is handled by 10 ex.domain.com.domain.com

# host -t mx domain.com
domain.com mail is handled by 30 ex.domain.com.

hmm... :-? did i misconfigured something?

Mr. C. · 10-15-2008, 01:46 AM

I can't give you any info about the webapp that configures your DNS zone files and named.conf file. if dig is giving the correct answers using your configured server, this is good confirmation.

Perhaps the other results are from recent cached resutls, not yet timed out?

Make sure you have A records for ns1.domain.com. and ex.domain.com. referenced in your zone file as;

Code:

                IN NS           ns1.domain.com.
                IN MX   30      ex.domain.com.

Yes, you should configure the rDNS side as well. It is trivial to do.

WorldIsNotFair · 10-15-2008, 02:00 AM

perhaps its not been updated on public dns like mr C posted, since you said that you migrate it from win2k box, when

exactly u migrate it ?

You should conf reverse dns, since nowdays some spam software use this method to confirm the sender domain.

hope help.

Jakarta heh,

aku jg jakarta hehehe.

romeo_tango · 10-15-2008, 03:15 AM

haha.. i didn't notice it earlier. jakarta toh..

anyway, yes, i just migrate it yesterday and perhaps i just need to wait yah. what made me confuse is that ex.domain.com.domain.com. Where do that come from..

about reverse dns.. after reading few helps, i guess i've got the point.. and am trying to configure it rite now.

Thanks

carlmarshall · 10-15-2008, 10:47 AM

Just a thought. Is the new serial higher than the old Windows one? I've seen windows use some very strange serial numbers for zone files.

Carl.