[bdNOG] Yahoo Mail can't communicate with my domain servers

Fri Dec 25 01:47:06 BDT 2015

53 port is filtered when request coming from remote though other service
ports are open to the host.Seems there is a application or firewall
level filtering to the port. 

>From remote server: 

root at server:~# nmap 103.9.185.229 

25/tcp open smtp
53/tcp filtered domain
465/tcp open smtps 

root at server:~# nmap ns2.aknetbd.com |grep 53
53/tcp open domain 

Thanks 

Suman 

On 2015-12-23 23:01, Brian Candler wrote: 

> On 23/12/2015 16:44, Jasim Alam wrote: 
> 
>> I understand this not a proper implementation. But this setup is running from years, until this week we didn't face any similar problem .
> 
> Then you have been lucky.
> 
>> Infact another domain of ours having ns boxes in same subnet not facing any similar issue.
>> 
>> [root at Jasim ~]# host -t ns btraccl.com
>> btraccl.com name server ns2.aknetbd.com.
>> btraccl.com name server ns1.aknetbd.com.
>> [root at Jasim ~]# host ns1.aknetbd.com
>> ns1.aknetbd.com has address 221.120.96.2
>> [root at Jasim ~]# host ns2.aknetbd.com
>> ns2.aknetbd.com has address 221.120.96.3
> You are also lucky that works. The fact that it works today does not mean it will work next week - nor that this is a good or reliable configuration.
> 
> RFC 2182 was written by people who really, really know what they are talking about. If you ignore their advice, your nameservice is liable to break in exactly the way you are experiencing. Don't say they didn't tell you :-)
> 
> "3.2. Unsuitable Configurations
> 
> While it is unfortunately quite common, servers for a zone should
> certainly not all be placed on the same LAN segment in the same room
> of the same building - or any of those. Such a configuration almost
> defeats the requirement, and utility, of having multiple servers."
> 
> If DNS is important to your business, isn't it worth paying $5 per month for off-site secondary? That would cover an unlimited number of domains.
> 
> Regards,
> 
> Brian.

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