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Forum Discussion

Amit585731's avatar
Amit585731
Icon for Nimbostratus rankNimbostratus
Oct 04, 2017

Automatic GTM failover

Hi All,   We are planning to deploy 2 GTM in delegate mode i.e. subzone for GTM managed wideip will be created on primary DNS server. The 2 GTM are in 2 different data center and requirement is al...
application delivery
BIG-IP
BIG-IP DNS
Simon_Blakely's avatar
Simon_Blakely
Icon for Employee rankEmployee
Oct 04, 2017

Your GTMs are referenced as the name servers for the delegated sub-domain. You either return both GTM ip addresses (in which case the client resolver will choose a nameserver from the supplied NS records), or only configure 1 NS record, and manually update this to direct traffic to the other nameserver.

 

Remember, the GTM that is queried for a wide IP does not influence the response address unless it is configured to do something different - in general, both GTM1 and GTM2 will return the same responses to DNS queries, so if GTM pool members (i.e. virtual servers in either DC1 or DC2) from DC1 are preferentially selected, both GTM1 and GTM2 will do so.

 

You have to strike a balance between reliability (having multiple NS server records for the sub-domain) and control over the destination of the traffic DC1/DC2. A manual failover operation to switch between DCs raises the risk of an interruption of service in an emergency, and you will need a short TTL on the SOA records, otherwise the failover change will take some time to propagate.