Simple DNS Plesk query please

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coolemail
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Simple DNS Plesk query please

Unread post by coolemail »

I want to create a DNS record remote.domain.com to be used for VPN connections. There are multiple ADSL/SDSL connections into the office each with their own public/static IP. Is it possible to set this up almost akin to the MX record system with a priority for multiple IP addresses? That way, VPNs could be set up with remote.domain.com and we can control the order that they will be connected to the various connections. Also, sometimes it might be good to load-balance so that two of the IPs could be on the same priority and thus have some VPNs going doen each route.

If all this is possible, can someone suggest the best way of doing it?

Many thanks in advance for a simple query.
Highland
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Re: Simple DNS Plesk query please

Unread post by Highland »

You can do this with something called Round Robin DNS. The basic idea is you would create an A record for each IP you want them to hit. Then you would set a low Time To Live (TTL) and simply rotate the order of the A records. Google does this with 6 datacenters at any given time (do a dig on google.com, wait 5 mins, then do another and you can see this in action).

I do not think Plesk supports this, however. I suppose you could edit the zone file for your domain (in /var/named/run-root/var) and change them manually, tho.
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coolemail
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Re: Simple DNS Plesk query please

Unread post by coolemail »

Thank You Highland for your response. That file reflects the DNS records we have put into Plesk for the domain.

So we are able to put in multiple A records with different IPs?

And having done that, the order that we amend them to in the /var/named/run-root/var/domain.com file is the order that they will look up that particular domain which will be remote.domain.com?

Is that right?
Highland
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Re: Simple DNS Plesk query please

Unread post by Highland »

Plesk will generate the file (I don't think it will regenerate unless you run a specific file) and then you can edit that file to your heart's content. Be sure to update the serial number.

Once you have the file edited, restart BIND to load the new file

Code: Select all

service named restart
The first A record usually wins.
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coolemail
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Re: Simple DNS Plesk query please

Unread post by coolemail »

Thank you Highland,

It is a shame that we cannot change the order of A records in the Plesk CP. How do I update the serial number? Do I make one up, or can this be done from the command line?
faris
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Re: Simple DNS Plesk query please

Unread post by faris »

Plesk does everything. All you do is add the A records in Plesk. Every time there's any change at all, Plesk changes the serials.

I suggest that you set up a new specific domain for this then change the SOA records via Plesk so you have a TTL of say 10 seconds. If you change the TTL on a domain used for web and email and stuff, a TTL of 10 seconds will cause pointless load on the DNS server and slow things down needlessly.

What I'm not clear about is your need for priorities and controlling the order and things? In theory, with RR-DNS, the incoming client connections will be spread evenly across all servers, though how evenly depends on how many servers and how many clients.

Also a VPN should not cause any significant load on your servers unless you are using them for file storage or something?

I'm not deliberately being nosey -- I'm just interested.

Faris.
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coolemail
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Re: Simple DNS Plesk query please

Unread post by coolemail »

The situation we have is as follows. One site has one SDSL line and two ADSL lines. SDSL is principally used for VoIP voice calls. One ADSL is much faster and wants to be the principal way in - default for computers. But when we are doing testing etc. and need to take it down then we want traffic to use the ADSL No2. If for any reason both those are down, they would use the SDSL as a last resort.

And/or we want to control the order (of IP addresses) that VPN connections will use with remote.domain.com to suit the need at the time.

So if we put multiple A records in Plesk, the question was whether we can control the order that remote.domain.com will use those multiple IPs.
faris
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Re: Simple DNS Plesk query please

Unread post by faris »

Ah. OK. The server has three IPs and is at the end of ADSL and SDSL connections. Got you. I had assumed the server was a box at a data centre sort of thing. I understand now.

This is essentially something you would normally do with IP routing rather than DNS. You see you can give weights to routes, and therefore do what you want.

It is not something I am knowledgeable about, though, and I can't even begin to guess the best way to implement it. It would probably involve a box in a data centre acting as a router, with three routes to the head office - or something along those lines.


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