The request was aimed at a server that can’t create a reaction. This can be sent by a server that isn’t arranged to deliver reactions for the blend of plan and authority that are remembered for the request URI.
Customers accepting a 421 Misdirected Request reaction from a server MAY retry the request – regardless of whether the request technique is idempotent or not – over an alternate association. This is conceivable if an association is reused or if an elective help is chosen ALT-SVC.
This status code MUST NOT be created by intermediaries.
A 421 reaction is cacheable as a matter of course, i.e., except if generally demonstrated by the strategy definition or express reserve controls.