irule for appending a URI to the URL

few options depending on if there are any more specifics to your use case. here are two:

when HTTP_REQUEST {
 HTTP::uri "/test/mypage"
}

or

when HTTP_REQUEST {
 if { [HTTP::path] equals "/" } {
 HTTP::uri "/test/mypage"
 }
}

Check out the iRules wiki for help with any other requirements. Loads of examples to help.

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