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The client receives a SERVFAIL when the CNAME queried to the BIG-IP DNS resolver takes more than the limit configured in the DNS Cache. The limit is set as 11 for BIG-IP v17.1.0 and later. It is fixed as 8 for earlier releases.
The clients cannot resolve DNS names if the count of the CNAME chases goes beyond the limit configured in the DNS cache.
A BIG-IP DNS is configured as a resolver (as a cache or a net resolver). The domain of which CNAME resolution is asked requires chasing more times than what is pre-configured in the DNS Cache.
The providers whose CNAME is queried can be asked to keep chains shorter than the pre-configured limits (the limits vary between different versions of BIG-IP).
A new DB variable sys db dnscache.maxqueryrestarts is introduced to allow configuration of the number of times the CNAME chase is performed.
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