After some more research I stumble upon "dns" options, and it turns out that setting up DNS server without enabling dns resolver option is no good.
And I can only make it good by re-running the setup command in order to make it stick in /etc/rc file.
But somehow it's not updating???
n3600a> dns info
DNS is disabled
n3600a> ping eccgw01.boulder.ibm.com
ping: unknown host: eccgw01.boulder.ibm.com
n3600a> options dns.enable on
** Option dns.enable is being set to "on", but this conflicts
** with a line in /etc/rc that sets it to "off".
** Options are automatically persistent, but the line in /etc/rc
** will override this persistence, so if you want to make this change
** persistent, you will need to change (or remove) the line in /etc/rc.
Sat Jan 22 18:44:11 SGT [n3600a: reg.options.overrideRc:warning]: Setting option dns.enable to 'on' conflicts with /etc/rc that sets it to 'off'.
You are changing option dns.enable which applies to both members of
the cluster in takeover mode.
This value must be the same in both cluster members prior to any takeover
or giveback, or that next takeover/giveback may not work correctly.
Sat Jan 22 18:44:11 SGT [n3600a: reg.options.cf.change:warning]: Option dns.enable changed on one cluster node.
