Solved

Adding CNAME record to DNS

Posted on 2009-05-19
13
976 Views
Last Modified: 2012-08-14
Hi,

I need to add a CNAME to an existing DNS record. The CNAME is facilities.domain.com

Should I add "facilities.domain.com" or "facilities.domain.com." [nb the period at the end]

I have heard that a period must be added at the end? Or is this if I only add "facilities", so that I add "facilities."?

0
Comment
Question by:kam_uk
13 Comments
 
LVL 5

Expert Comment

by:Neranel
ID: 24425917
a FUlly Qualified Domain Name always ends with a period.  
"facilities.domain.com."
If you are using microsoft DNS, it will add the period for you, so you really dont need to worry, but the correct way is with the period.
Though you should really only need to add 'facilities' to the 'domain.com' zone.
0
 
LVL 1

Expert Comment

by:ElloDarkstar
ID: 24425943
It may depend on where you're adding a dns record, but most registrars I know of have ways to avoid issues (they request only the host name, then fill in the domain and extension for you).
0
 
LVL 3

Author Comment

by:kam_uk
ID: 24426052
Thanks guys - out of interest - why do we add the period at the end, what does it perform?
0
 
LVL 5

Expert Comment

by:Neranel
ID: 24426066
. is the root internet domain
so com is a subdomain of .
0
 
LVL 3

Author Comment

by:kam_uk
ID: 24426093
sorry, i don't understand :(

I'm not a DNS expert by any means
0
 
LVL 5

Expert Comment

by:Neranel
ID: 24426510
a domain name like test.yahoo.com is actually 4 domains
first, remomber that i said all domains end with a period if they are fully qualified?
so now we have test.yahoo.com.
let me break it out
test (is a subdomain of) Yahoo (is a subdomain of) com (is a subdomain of) .
. being the root everything bucket domain of the entire internet.
0
DevOps Toolchain Recommendations

Read this Gartner Research Note and discover how your IT organization can automate and optimize DevOps processes using a toolchain architecture.

 
LVL 5

Assisted Solution

by:Neranel
Neranel earned 200 total points
ID: 24426636
So to understand, when you dns server is questioned about who is test.yahoo.com it starts at the biggest.
.
it asks a root name server, who is test.yahoo.com.
the root server says, i dont know, but i know com's nameserver is x.x.x.x (now referred to as com NS)
so the DNS server asks com NS who is test.yahoo.com.
the com NS server says i dont know but i know yahoo's NS is y.y.y.y (now yahoo NS)
so the DNS Server asks yahoo NS who is test.yahoo.com.
and the yahoo NS says test.yahoo.com. is at ip addres z.z.z.z
 
Does that help?
0
 
LVL 3

Author Comment

by:kam_uk
ID: 24426677
Yep, helps a lot..

Just one more question :)

What is the effect of not adding the .

0
 
LVL 5

Expert Comment

by:Neranel
ID: 24426717
in most cases the software will handle it for you.
0
 
LVL 3

Author Comment

by:kam_uk
ID: 24426761
sure, but what if it doesn't - i'm just curious that's all :)
0
 
LVL 5

Expert Comment

by:Neranel
ID: 24426918
Then you would need to.
0
 
LVL 70

Accepted Solution

by:
Chris Dent earned 300 total points
ID: 24429878

Everything in a zone file is relative to the origin (zone file name) unless explicitly terminated.

That is, if you fail to include the terminating period on a record in a DNS zone (and the software doesn't do it) the current zone name will be appended to the record.

For instance, if you have this, with an omitted period:

somezone.com.
   host1   IN CNAME   otherhost.otherdomain.com
   host2   IN CNAME   otherhostinthisdomain

You end up with this when you lookup host1:

otherhost.otherdomain.com.somezone.com.

And this when you lookup host2:

otherhostinthisdomain.somezone.com.

This occurs because of the short-hand conventions allowed when creating Zone Files for a DNS server. The same occurs with the "host1" entry. Because it doesn't have a terminating period it has the zone name appended and and becomes "host1.somezone.com.".

If all records were written in the longer form (with the correct termination this time) we would have:

somezone.com.
   host1.somezone.com.   IN CNAME   otherhost.otherdomain.com.
   host2.somezone.com.   IN CNAME   otherhostinthisdomain.somezone.com.

The zone file is less flexible, it's specific to "somezone.com", if it were all written in the short-hand form you could pick up the zone file, call it otherzone.com and it would happily answer requests. e.g.:

otherzone.com.
   host1   IN CNAME   otherhost.otherdomain.com.
   host2   IN CNAME   otherhostinthisdomain

Chris
0
 
LVL 5

Expert Comment

by:Neranel
ID: 24477574
Did we answer your Questions?, If not what DNS Platform are you using? If we did, can you please close the question.
 
Thank You,
Neranel
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

There have been a lot of times when we have seen the need to enter a large number of DNS entries in a forward lookup zone. The standard procedure would be to launch the DNS Manager console, create the Zone and start adding new hosts using the New…
BIND is the most widely used Name Server. A Name Server is the one that translates a site name to it's IP address. There is a new bug in BIND (https://kb.isc.org/article/AA-01272), affecting all versions of BIND 9 from BIND 9.1.0 (inclusive) thro…
Get a first impression of how PRTG looks and learn how it works.   This video is a short introduction to PRTG, as an initial overview or as a quick start for new PRTG users.
You have products, that come in variants and want to set different prices for them? Watch this micro tutorial that describes how to configure prices for Magento super attributes. Assigning simple products to configurable: We assigned simple products…

932 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

9 Experts available now in Live!

Get 1:1 Help Now