How to setup DNS failover for external users to use FTP, VPN or Email?

dickchan
dickchan used Ask the Experts™
on
We have two broadband from two Internet Service Providers.
Is it possible to have have HA or Fail-over if main broadband service is down?

Any  impact if we create one A record with multiple IP?
I worry that if main broadband down, some external users may fail to auto switch to use second IP due to the DNS renewal interval and cache.
We do not have own external DNS server and domain record is hosted at vendor.

Any advise?
Thank you.
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Commented:
If you have CISCO devices then try configuring HSRP or VVRP or GLBP.
Commented:
What you describe, is called Round Robin and you will not get any high availability, but you will get 50% hits to your second IP.

What it means, is that each time the DNS server hosting the record gets a query for server.com, it will provide IP1 first. Second time the DNS server is getting a query for comapy.com, it will provide IP2. And than it starts again. So that means it is good for load balancing, but the DNS server has no idea that IP1 is down, so it will still provide IP1 for 50% of the queries.

A better solution (and more automated), would be to have a firewall/router on your network that supports BGP and setup BGP routing with both your internet providers. In case primary connection goes down, the second is taking over instantly (typically less than 5 seconds) without any admin work, it happens automatically.

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