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[VNX-for-File Replication] DDNS updates and TTL
I'm testing a fail-over scenario. I switch over a specifiv virtual datamover and it updates its DNS entry with a DDNS update operation. This resets also the DNS TTL for the specific entry to the default value (20min). This causes troubles to the connected clients. Is there any option on the VNX to update also the TTL on the DNS? Or any workaround? thanks
Rainer_EMC
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November 27th, 2014 09:00
Why trouble ?
matteo_marchett
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November 27th, 2014 09:00
DNS servers are two Windows machines and they take a "while" (TTL time I suppose) to sync.
During the sync period, from a client pc I get (randomly) the old or the new ip address.
In my infrastructure the "main" DNS server is a physical appliance which is forwarding the requests to these Windows boxes.
Does it make sense?
Peter_EMC
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December 1st, 2014 04:00
Microsoft is using the word replication for updating DNS servers in a AD.
This is a problem of the domain which can not be fixed by the VNX during the failover.
If a client is getting a DNS answer immediately before the failover, this client will use this information till its TTL.
So, if the VNX will update the DNS during the failover, it is already to late to change anything for the client who got it´s answer before.
From the using VNX replicator manual:
"In most CIFS data-recovery configurations, your network addresses (IPs) change because
your data recovery site resides in a different subnet. Windows Server 2000 with dynamic
DNS masks this change from your clients. Using UNC pathnames, when the VDM is loaded,
the CIFS servers dynamically declare in the DNS and the records are updated as soon as
they start up on the destination site in a failover.The speed at which these changes propagate
through the DNS servers used by your clients depends on your environment.
If you want to retain the same IP addresses on the destination site in a failover, you may do
so, but you will need to configure your interfaces on the destination site and they must be
down until you are ready to activate the destination site."
This is not only a TTL issue, but also a question of the speed of the DNS replication across all DNS servers