What are the HA Heartbeat and Hello Messages?
Resolution
Overview
There are two types of messages are sent between peers when HA is enabled. The Control Link (HA1) communicates over a TCP connection. The first is the 'Hello' message. The second is the 'Heartbeat' message.
Hearbeat Message
The 'Heartbeat' message is an ICMP Ping that is sent to its peer every configured 'Heartbeat Interval'. It verifies network connectivity with the HA peer.
Hello Message
The 'Hello' message is sent from each peer to the other once every configured 'Hello Interval'. It determines if the HA Agent is running. No response is sent by the recipient. This message is also sent if there is a HA state change or other informational changes are needed. This message communicates:
- HA state of the device
- Device Priority
- HA2 (Data Link) cookie
- If the 'ha_lib' connection is seen locally ('sysd' peer connection)
It will also send this information when it has changed:
- If 'Config Sync' is enabled
- Config MD5SUM (to know if we are in config sync)
- When a commit fail has occurred
- Time sync if you push the time from the local to the peer
owner: jdavis