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how do I create a record on my DNS server or host record that would point a FQDN to 2 different IP address?

Posted on 2004-11-26
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Last Modified: 2010-04-10
Hello,

how do I create a record on my DNS server or host file that would point a FQDN to 2 different IP addresses? The reason is I am trying to setup a redundant tunnel for my branch offices. The branch offices need to connect to VPN.Mydomain.com at all times no matter which link was down. Currently one of my branch offices cannot reach vpn.Mydomain.com (The get "Unknown host" message when trying to ping the name) so I was told to create A records or to modify the host file. The only thing is A records only let you create one ip to one name. Please help.
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Question by:Steviek411
7 Comments
 
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Expert Comment

by:grblades
ID: 12682992
Hi Steviek411,
You can create multiple name/A record entries using the same name.
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Expert Comment

by:lrmoore
ID: 12683125
You can create multiple A records with different names to different IP addresses, then create multiple CNAME records that point "VPN" to multiple different A records.
For example:
vpn1 A 1.2.3.4
vpn2 A 4.3.2.5
vpn CNAME vpn1
vpn CNAME vpn2

Beware that DNS is not intelligent enough to answer with the one that is currently "up", it will round-robin the answers.
If you're looking for a solution that only provides the alternate IP if the first one is "down", then you're looking for a non-DNS answer - something like Cisco's distributed director function...
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Author Comment

by:Steviek411
ID: 12683151
Is there a way doing this by editing the Hosts file instead of using DNS?
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Expert Comment

by:lrmoore
ID: 12683212
You can have multiple entries in your hosts file, but it still won't help if the first one is dead. The first entry of the hosts file will be cached...
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Author Comment

by:Steviek411
ID: 12683268
Ok the example you gave
vpn1 A 1.2.3.4
vpn2 A 4.3.2.5
vpn CNAME vpn1
vpn CNAME vpn2

How would I do this if I only have one name. For example i have
VPN.domain.com A 1.2.3.4
VPN.domain.com A 9.8.7.6

How would the CNAME look?
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Accepted Solution

by:
marcin79 earned 300 total points
ID: 12683346
as far i understand the problem is that you have 2 lines to THE SAME network (ex. vpn through two different providers) The question is why do you want do it by dns entries and not by routing ?
IMHO it *could* be difficult to do a one-name-2ip's solution. I would rather preffer a routing solution - so if one link is down try to use another link.

other solution:
CNAME and A record relay on the dns server, so if the dns is down on the one link you don't have a dns server at all.  YOU COULD try to set up a two dns servers with TWO DIFFERENT A entries one on the *end* of the first link and the second on the *end* of the second link. Both of them should be a master of specified zone. then you should enter according entries in the one and seccond dns servers (depending on the link). Then on the clients machines you should enter as the primary dns (more reliable) and the second one as the slave one.

BE AWARE that this is a very dangerous solution and if you will not maintain those two servers properly this *may* cause serius problems.

Hope this helps

Regards
Marcin
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LVL 79

Assisted Solution

by:lrmoore
lrmoore earned 1200 total points
ID: 12683573
Given this:
  VPN.domain.com A 1.2.3.4
  VPN.domain.com A 9.8.7.6

You have two options. Leave it as is with two A records to two different IP's
or create a CNAME
  VPN1.domain.com A 1.2.3.4
  VPN2.domain.com A 9.8.7.6
  VPN.domain.com CNAME VPN1.domain.com
  VPN.domain.com CNMAE VPN2.domain.com

What version VPN Client are you using? Many of them have a built-in facility for a backup IP address (Cisco's for example)...


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