DNS Replication ? 1

[bluntbill]

I am not sure this thread should belong in this forum...

But since I didn't know where to post it, here it goes:

I have a server with some sites hosted in it. I have a fixed IP internet connection. I want to get a second one so the hosting will stay up if the first connection drops dead. How can I get the dns resolutions to point both to my first and second IP addresses? And change from one to another if one of the connections fail? Is this done with dns servers installed on my box? Is it possible to get this done?

Thank you for your help

 

[Grenage]

I believe what you want is something called a "DNS round robin". There are companies out there that can set such things up for you, for a small fee.

For example, they constantly check for connectivity on your primary IP address, if it fails, they change the A record to match your secondary IP address.

Carlsberg don't run I.T departments, but if they did they'd probably be more fun.

 

[chipk]

Round Robin is really for load balancing, not Distaster Recovery. If one server goes down, it is not smart enough to stop sending requests to that server.

You may consider a clustered solution for high availability, or do something creative to change the IP on the "backup" box if a failure is detected on the primary. That could get a little touchy, though, so you have to be careful.

 

[Grenage]

True, the exact term isn't "round robin" for what I mention, but similar. There are definitely providers out there who will host the service for a small fee. I will find a link to one of the companies, if I ever find it again!

Carlsberg don't run I.T departments, but if they did they'd probably be more fun.

 

[lgarner]

DNS round robin should work, but it's due to browser behaviour rather than DNS. As I recall reading and from some basic testing, browsers will try to look up site more than once if the site is down. Having 2 A records should then provide the good address to those who initially connected to the bad one, though those users would experience a delay as if the site was slow.

 

[JBAS]

There is a few ways of sorting the problem out, such as implementing certain Disaster recovery tools...
A good one is a system that will perform real-time monitoring and failover of a pecific IP address usually associated with a content server, for example;
If the service monitors detect a failure of IP 1.1.1.1, it will automatically fail over to IP 1.1.1.2

As mentioned in a few threads below/above certain companies can offer this service for next to nothing.

Good luck

 

[bluntbill]

I don't know if that's exactly what I need.

For example, imagine a company xpto.com which hosts other sites. that company has a primary IP address to where ssh, web, ftp and other requests are forwarded to. if their connection fails, there must be a way for the site to still be visible (like in dns, where you have primary and secondary server in case one fails).

What I thought was: 2 machines, 1 with each connection, and DNS serves on both. Each of the web sites I have hosted should have their primary and secondary dns servers as my two machines with the 2 different IPs. If the main connection fails, any request to any of the domains is forwarded to the secondary dns server, which points out the machine that has the pages hosted (with lan address that remains available).

I don't know if I explained myself correctly and if this method works...Please let me know.

Thank you

 

[JBAS]

It sounds like you need something as i highlighted on friday, if i understood your queries right.

It would be a Failover solution of a basic nature set on both your main IP adresses.

That will ensure that no matter what happens you can keep 24/7 access to your site.

 

[bluntbill]

that's exactly what I want.

Does my approach work? Is it correct and the most efficient way of doing it?

 

[bluntbill]

By the way, I can do this with only one machine right?

It isn't as failproof as with two machines, but serves the same purpose for the internet connectivity, i think. if I have two ethernet ports, each connected to a different connection, and for example 2 vservers, each of them assigned to one of the ethernet ports, both of them with dns server installed, and the other services could be all in another vserver right?

thank you

 

[JBAS]

Hi again

Your approach would work, however it seems long and complicated whereby you could set up this failover system on both main address.

The beauty of it is that within the managed interface you an set up the time interval let it be 2 min, 5 or 15 to actually monitor the same by sending out a ping (under what ever set up) and if it doesn't come back or detects even a bit of latency it will auto failover to the secondary adress
The same applies to the other IP adress.
Generally you will be looking at one system per main domain/IP

The system i'm talking about however cannot be set up on BIND, but having said that i'm sure that a similar set does exist, but i don't know where you could get it.

The product i'm talking about is what we specialize in, but due to the rules of this site i do not know if i can pass you the info?

 

[bluntbill]

the system you're talking about provides failover and load balancing, for what you have explained.

At the moment, what matters most to me is the cost of getting it done. With the solution I presented, my only cost will be the extra connection, because I can implement all the software I need in the same machine with vservers (although the second connection will be rarely used - at least it's what I expect lol). Do you know if my apporach has any downside? I don't want to spendthe money if it doesn0t look like working out fine...

Thank you again

 

[JBAS]

That is right.

I don't see or seem to highlight any downside, as long as u implement the whole system as per the way it was discussed.
Make sure you do get the most in terms of testing and i would advise to do a test as well.
If you are connecting to a secondary server unsure the same is always operational or perhaps if you have the facility try failover to a live one....it's entirely up to you....
Cost point of view your idea make's sense, i can tell you that for a system as i decribe you looking around $200, so if only the connection is going to cost you...go for it...
Hopefully you wont really need it (lol)
Let me know if i can help you with anything else to do with DNS and i will gladly advise you.
Good Luck

 

[bluntbill]

i didn't understand what you said here: "If you are connecting to a secondary server unsure the same is always operational or perhaps if you have the facility try failover to a live one....it's entirely up to you...." sorry but i'm not from an english speaking country and sometimes it's hard for me to understand...lol

It will take some time for the internet to get installed but I will post the result here when it's done, and I will almost for sure have some doubts about dns, so I'll be back.

Thanks a lot.

A star for you

 

[JBAS]

No problems, you are welcome.

What i meant is that there is two ways you could failover that i know off;
1. The secondary IP could be held on a different server which is live and is currently in use in terms of traffic going to it

2. or you could failover to a secondary IP on a back up server which only kicks in for those matters.

I hope it makes sense, that is the way a client of mine was handling his case.

Take care and all the best.

 

[bluntbill]

ok so let's see. What I had in mind was the second option, but it would rarely use the second connection, which is not good.

Tell me if this is possible: I have multiple domains hosted by a company. I can edit their dns records, to put my own dns servers. If I put for example, on 5 domains my primary dns as ns1.mydomain and the secondary as ns2.mydomain and on other 5 domains I do the reverse, setting my primary as ns2.mydomain and secondary as ns1.mysomain. Can I do this? And will this balance the traffic for the domains? I understand that it's not a good load balancing because one of the sites can have 90% of the traffic, but if it works, it's better than nothing...

 

[JBAS]

That is avery rudementic way of doing it, the thing is that at a quick glanse like you said you can't really load balance properly, it will work but you won't have control really of where to direct the traffic.
When you can and have got budget i would recommend to either get Geographical LB or % LB, than you are in complete control of it.

Having say that in your case, i think that perhaps the server with 10% could be used as the backup one and you will know that it is live by getting constant traffic to it (which you will still have to monitor in any case)

Does it make sense?