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Cisco Bug: CSCup89922 - ASA DNS lookups always prefer IPv6 response

Last Modified

Nov 27, 2020

Products (2)

  • Cisco Adaptive Security Appliance (ASA) Software
  • Cisco Adaptive Security Appliance (ASA) Software

Known Affected Releases

9.1(0.2) 9.1(1) 9.1(5)

Description (partial)

A DNS server configured on the ASA will always use IPv6 DNS requests 
(type=AAAA) if any of the interfaces are configured with IPv6. There is 
no way to prevent this behaviour, or make the ASA prefer and sending 
type=A requests.

This only occurs if IPv6 is enabled on any interface of the ASA, even if no Globally Unique Address is assigned. If IPv6 is enabled, then the ASA only makes Type=AAAA DNS requests. This will always result in an IPv6 DNS response, and potentially cause features that depend on DNS to fail (ie. Smart Call Home).
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Bug Details Include

  • Full Description (including symptoms, conditions and workarounds)
  • Status
  • Severity
  • Known Fixed Releases
  • Related Community Discussions
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