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Cisco Bug: CSCvs39104 - IOS XE need a knob to prefer ipv4 over ipv6 dns response for ios DNS client

Last Modified

Dec 10, 2019

Products (1)

  • Cisco IOS

Known Affected Releases

16.9.4

Description (partial)

Symptom:
When a CAT9400 is trying to communicate to tools.cisco.com to install the smart license, it first tries to resolve the hostname sending a dns query and gets a dns response back from the DNS server, however, since the interface is configured with both IPv4 and IPv6 addresses the switch prefers to use the ipv6 and since their ISP does not support IPv6 it fails.

Conditions:
The customerĀ“s LAN network is IPV6 however the ISP does not support it.
The CAT9400 is configured with  "ip http client source-interface interface" command and the interface in question uses an IPv6 address and an IPv4 address. 
Because of the mentioned above, it establishes a session with IPv6 connectivity and it fails.
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