If you are new to NuttX probably already noticed that sometime the first ping to a new IP is lost, right?

nsh> ping 10.0.1.2
PING 10.0.1.2 64 bytes of data
No response from 10.0.1.2: icmp_seq=0 time=1000 ms
64 bytes from 10.0.1.2: icmp_seq=1 time=6.8 ms

I asked that question at this PR: https://github.com/apache/nuttx/pull/9254 and got the response directly from the father of NuttX, Mr. Greg Nutt:

I don't know the current state, but in the past the first ECHO REQUEST packet was not sent because the MAC address of the destination did not appear in the ARP table (IPv4 or neighbor table for IPv6). So instead of sending the ECHO REQUEST, and ARP requests was sent instead.
If that is the problem it can be eliminated for IPv4 by selecting CONFIG_NET_ARP_SEND. For IPv6, the similar setting is CONFIG_NET_ICMPv6_NEIGHBOR, I think."

So, that is it, if you want to get rid of this error message, just enable CONFIG_NET_ARP_SEND