ERR_NOOPERHOST (491) numeric is sent to users who try to use the
OPER command, only to be rejected because the server doesn’t allow connections from the client’s host to become operators. In other words, when the server’s configured to only allow oper-ups from specific IP addresses/networks, and the user’s current network doesn’t fall within the server’s allowed range.
:server 491 <nick> :No O-lines for your host
<nick>: Nickname of the user.
The final parameter’s text is human-readable and may vary, but the message is typically something like the above.
C: OPER dan :my cool passphrase S: :irc.example.com 491 dan :Only few of mere mortals may try to enter the twilight zone
An example of an oper attempt being rejected.
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Latest change: 30 November 2018.