iRule Shenanigans - My Brain hurts

JustCooLpOOLe I see the issue with your iRule and it's both in the if statement and switch statement. For the if statement where you look at the HTTP::host you are matching it to "/" which will never match because host names do not have a "/" in them. The issue with the switch statement is that you are not matching against any particular value denoted by "switch {" which isn't matching against anything in particular. Based on the iRule that you have in place it doesn't seem as though you are matching on a host at all and are just concerned with the URI path so the following iRule should work for you. In conjunction with this iRule you should consider configuring a OneConnect profile so that every HTTP request is passed through the iRule rather than just the initial HTTP request when the TCP connection is formed. I would also like to note that the iRule that you provided does not match what you put in your original post so if what I have provided this time doesn't meet your needs could you provide additional information on what you are attempting to achieve?

when HTTP_REQUEST priority 500 {

    set HOST [HTTP::host]
    set URI [string tolower [HTTP::uri]]

    switch -glob -- ${URI} {
        "/" {
            HTTP::redirect 301 Location "https://${HOST}/mainpage.html"
        }
        "/mainpage.html" {
            HTTP::respond 200 content [ifile get "mainpage.html"]
        }
        "/mylogo.jpg" {
            HTTP::respond 200 content [ifile get "mylogo.html"]
        }
        default {
            drop
        }
    }

}