NSLOOKUP from the regular command line requires
5770SS1   31       5050    Domain Name System
However, if it fails, and you have 5733SC1 loaded (required) then you may need a PTF.  I needed this PTF on all of my lpars which had 5770SS1-31.
NSLOOKUP HOSTNAME('10.10.6.144')
Could not load dependent PASE for i module libcrypto.so.1.1(shr.o).
Cannot load PASE for i module libcrypto.so.1.1(shr.o).
Internal system error.  Error code is 2.
Error loading PASE for i program
  /QOpenSys/QIBM/ProdData/OS400/DNS/bin/nslookup.  See previous messages.
SNDPTFORD PTFID((SI70819))
PTF 5733SC1-SI70819 V7R2M0 received and stored in library QGPL.
INSPTF LICPGM((5733SC1)) INSTYP(*IMMDLY)
PTF 5733SC1-SI70819 V7R2M0 loaded into library QUTL.
PTF 5733SC1-SI70819 V7R2M0 temporarily applied to library QUTL.
ENDTCPSVR SERVER(*SSHD)
STRTCPSVR SERVER(*SSHD)
NSLOOKUP HOSTNAME('10.10.6.144')
Works fine now.
Rather pervasive.
Another option is the following but it didn't apply to any of my situations.
https://www.ibm.com/support/pages/nslookup-name-or-ip-results-error-messages-cpdb9ea-cpdb9c1-cpdb9c9-cpfb9c0
Rob Berendt
--
IBM Certified System Administrator - IBM i 6.1
Group Dekko
Dept 1600
Mail to:  2505 Dekko Drive
          Garrett, IN 46738
Ship to:  Dock 108
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          Kendallville, IN 46755
http://www.dekko.com
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