3 DSL connections, 1 loadbalancer, virtual IP?

Let me attempt to explain this to see if its technically possible...

Current set-up:
3 DSL connections with multiple static IP's.
Each DSL router has the first static IP from each respective range.
DSL routers connected to 3 WAN ports on draytek v3300 load balancer.
Each v3300 has the second IP on each respective range - thus can be accessed externally using each connection.

Question:
Can this be set-up in such a way that allows remote connection (RDP, whatever) in on ONE address/hostname, even if one or two connections drop, they can still access the internal server without having to change IPs.

Answers on a postcard..or alternatively a reply

http://en.wikipedia.org/wiki/Round_robin_DNS

Sounded good until I got to this bit..

" If a service at one of the addresses in the list fails, the DNS will continue to hand out that address and clients will still attempt to reach the inoperable service."

So I could setup the DNS records as follows:

domain.com

rdp A 1.1.1.1
rdp A 2.2.2.2

Therefore I could RDP to rdp.domain.com and come in one 1 of the 2 connections in a round robin fashion. However if one of the links fails, the DNS will still hand out the failed connections IP.

Not an expert on this, but IIRC Round Robin is a cheap way of achieving a form of load balancing by sending clients to each of a range of IPs in sequence. So it distributes load (though not in a measured way nor by taking account of actual load per server, just "take it in turns") but is not a high availability solution.

I think this needs to be at the DNS level, so it's the right place to start, doing it manually you'd just need to set a short TTL (Time to live) for your A records and in the event one IP drops offline you can remove from the list / change the A record.

If you're looking for that to be automatic - as in a high availability setup - I think you might need to have the load balancer at the network level - for example in a data centre with 3 servers, you'd have the load balancer on the local subnet with the 3 servers behind it. When one thing on the circuits stops responding the load balancer drops that destination and balances the others.

But unless you can get some sort of specialised DNS service which is linked to an availability monitoring service which does the "manual bit" above, automatically (and even then, proxies en route ignoring the TTL could be an issue) I'm not sure how it can be done over three separate networks.

I think. Hopefully someone else can help out here.

Example of monitoring/alerting service

http://alertra.com/features.php

Has escalation features, but not (as far as I can see) automatic DNS changes.

Yeah, I thought you said there are 3? You would have a 1 in 3 chance though and the next one after a failing one would work

If someone is attempting to the connect and gets given the failed over IP, obviously they cannot connect, however if they retry immediately, they should in theory get one the the next in the round robin list?

That's how it works.

Your sig is putting me off btw

Can you put the name servers at the three connections.

If one connection fails then the DNS will not respond and users will get the next one.

The name server records have to be different each directing the traffic to its own connection.