Pool selection using iRule

If you specify POOL-1 as the default pool, then I'd use the last iRule like this:

when HTTP_REQUEST { 
    log local0. "Host: [HTTP::host]"
    log local0. "URI: [HTTP::uri]"
    switch -glob [string tolower [HTTP::uri]] { 
        "/" {
            log local0. "  /: Redirect to /123/456"
            HTTP::redirect "/123/456"
            return
        }
        "/999/*" {
            log local0. "  /999/*: Pool POOL-2"
            pool POOL-2 
        }
    }
}

If you're having trouble with request, then you could check it from the CLI using

curl

curl -k https://:/123/546 -v