dns failover

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Apr 1st, 2008
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I want to let url's in Callmanager work with dns-names instead of ip-addresses for failover reasons. In my dns-server (Windows Server 2003), I'v created 2 A-records with the same name, but a different ip-address (thus name1 =, name1 = This doesn't seem enough, because when I is down, pinging to name1 still results in a ping to instead of What should I do ?

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lloyd.johnson Tue, 04/01/2008 - 10:31
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use uniquie dns names for your callmanagers.

exs cm-pub.domain.local and cm-sub.domain.local. set up a call manager group in call manager and place both call managers in that group and assign it the device pool that the phones are using. You should see both call managers in the phones network settings

kthorngr Tue, 04/01/2008 - 18:00
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  • Cisco Employee,

The problem is with DNS caching. A DNS record has a TTL (Time to live) value that specifics how long a device is allowed to cache the record. For example, if the A Record has a TTL of 1 then the client device that requests the record should age the entry after 1 minute. You mileage may vary depending on OS and application. Some behave correctly and others do not.

If this is a critical application then your best option is to use some sort of server load balancing.



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