# NSRP Link

You can configure a device to monitor the status of a HA link by sending NSRP probe requests on the HA link to its peer. If a reply is received from the peer on the HA link, the request is considered successful and the HA link is assumed to be up. If no reply is received from the peer within the constraints specified, the HA link is considered to be down. This enables devices to switch transmission of control messages to another HA link if available, even if there is no physical failure on the HA ports on either device.

By default, the device sends probes on all HA links once every second. (You can optionally specify the HA zone interface and the interval at which probes are sent.) By default, if five consecutive probes are sent without receiving a reply from the peer, the link is considered to be down; you can specify a different threshold value for determining when the link is down.

Note that even when a primary HA link is down, the device continues to send probes on that link. If the primary HA link connection is restored and peer responses are once again received on the link, the devices can switch transmission of control messages back to the primary HA link.

Note: You can send probe requests manually using the CLI only: exec nsrp probe ha_interf count number.

### To Configure Automatic HA Link Probing

Enter the following information, and then click Apply to save your settings:

Secondary Link: (Optional) Specify the interface on which the device sends VSD heartbeats if the primary HA link goes down.

Enable HA Link Probe: Select this option to enable HA link probing to monitor the state of the HA link.

Interval: (Optional) Specify an interval of time in seconds at which the device sends probes to its peers. The range is 1 - 100 seconds. The default is 1 (that is, every second).

Threshold: Specify a threshold value for determining when the link is down. By default, if five consecutive probes are sent without receiving a reply from the peer, the link is considered to be down.

Control Link: (Read-only) Indicates the state of the HA control link. The high availability messages contain the information that enables the backup to become the primary without causing a service interruption.

Data Link: (Read-only) Indicates the state of the HA data link. Data messages are IP packets traversing the firewall that must be forwarded from the backup in a VSD group to the device acting as primary.

Secondary Link: (Read-only) Indicates the state of the secondary link (up or down). If both the HA1 and HA2 links are lost, then the device can send VSD heartbeats through the interface specified as the secondary link.