To get ARP entry, using the REST API, if the <ip_address> is not in the switch's ARP table, then get an Exception error message.

curl --user "admin":"admin" -H "Accept: application/json" -H "Content-type: application/json" -X POST http://<controller_ip_address>:8181/restconf/operations/misc-config:get-arp-entry -d "{input:{"node-id":<node_id>, "ip-address":'<ip_address>'}}"

Client get error:

<p>Problem accessing /restconf/operations/misc-config:get-arp-entry. Reason:
<pre> Server Error</pre></p><h3>Caused by:</h3><pre>java.lang.NullPointerException
at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:210)
...