DNS PTR Question
Daniel B. Thurman
dant at cdkkt.com
Wed Feb 24 21:59:15 UTC 2010
On 02/24/2010 01:19 PM, James Wilkinson wrote:
> Daniel B. Thurman wrote:
>> I am trying to get a handle on how to properly
>> assign DNS PTR records, given these conditions:
>>
>> 1) Single machine containing:
>> a) DNS Server
>> b) Sendmail Server
> <snip>
>> The problem here is assigning the PTR, since
>> only ONE reverse IP address is allowed. In
>> the above case, which will it be, ns1.domain.com
>> or mx1.domain.com? Discovery led to the last
>> "scanned" entry, which is mx1.domain.com
>>
>> Why is this a potential problem?
>> + One that I can think of, is security verification
>> such as some programs do a reverse IP check to reduce
>> phishing/spamming?
>
> Alternate idea: have both mx1 and ns1 as CNAMEs to the “real” host name,
> and put that “real” host name in the reverse DNS.
>
> Don’t forget that you have to have your MX records pointing to that A
> record: MX pointing to CNAMEs is Not Allowed.
>
> Hope this helps,
>
> James.
>
So, basically you are saying this?
Forward zone contains:
======================
$TTL 172800
@ IN SOA host1.domain.com. admin.domain.com. (
3818 ; serial
3H ; refresh
15M ; retry
1W ; expiry
1D ) ; minimum
; ==========[Nameservers]=================
@ IN NS host1.domain.com.
; ==========[Mail Exchangers]=============
@ IN MX 10 host1.domain.com.
; ==========[Machines]====================
ns1 IN CNAME host1.domain.com.
mx1 IN CNAME host1.domain.com.
host1 IN A 10.1.0.1
[...]
Reverse zone contains:
======================
$TTL 172800
@ IN SOA ns1.domain.com admin.domain.com (
3818 ; serial
3H ; refresh
15M ; retry
1W ; expiry
1D ) ; minimum
;============[Top-Level]==================
@ IN NS host1.domain.com.
;============[PTRS]=======================
1 IN PTR host1.domain.com.
[...]
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