HA is not working on NetScaler and the following error message is displayed:
Secondary node was down and peer device was Unknown

Unable to find the peer device in HA configuration.

1. Checked the configuration; 0/1 interfaces was down but enabled.
2. Asked to plug interface 0/1 and was able to find the peer device.
3. Verified the configuration and could find interface 1/4 and 1/5 which were up and enabled. These were sending tagged traffic only.
4. There was no interface to send untagged traffic or native vlan traffic.
5. Asked to create an untagged traffic or create an access port which can send untagged traffic.
6. After creating access port on switch, we were able to send the untagged traffic and peers were able to find each other.