Switch Discovery in an Availability Pair

When configuring ExtremeXOS switches in an ExtremeCloud IQ Controller (ExtremeCloud IQ Controller) Availability Pair, use an "A" record for extremecontrol@<domain-name>, providing an IP address for the primary ExtremeCloud IQ Controller and an IP address for the backup ExtremeCloud IQ Controller. When the first address fails, the switch attempts the second IP address. If both IP addresses fail, the switch performs a second DNS request. The switch performs the DNS request before sending an HTTPS message and does not use DNS caching.

• If both the primary and backup ExtremeCloud IQ Controller are up, all configured switches are adopted on the primary ExtremeCloud IQ Controller, and the switch sends the HTTPS message to the primary ExtremeCloud IQ Controller only.
• If the primary ExtremeCloud IQ Controller is down and the backup ExtremeCloud IQ Controller is up, the switch fails over to the backup. The switch will timeout on the primary IP address and proceed to the secondary IP address. The switch attempts to send the HTTPS message to the primary ExtremeCloud IQ Controller first because its IP address is first in the DNS reply. That attempt will timeout and the switch will send the second HTTPS to the secondary IP address. The switch continues to send HTTPS messages to both IP addresses. If the primary ExtremeCloud IQ Controller comes up, the switch sends the HTTP message to the first IP address and does not attempt the second IP address.