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Icon for Nimbostratus rankNimbostratus
Apr 23, 2019

iRule to drop connection of invalid host header

I have an issue creating an iRule. I need the iRule to drop the connection at the F5 if the host header is manipulated. I have tried some iRules in Test but the syntax is apparently not correct.


1 Reply


    try the iRule to allow just a few selected HOST-header values to pass through...

    when HTTP_REQUEST {
        switch -exact -- [string tolower [HTTP::host]] {
            "" -
            "" -
            "" {
                 Do nothing for white listed HOST-header values...
            default {
                 Send 502 response for reuqests with unknown HOST-headers...
                HTTP::respond 502 content "Bad Gateway" "Content-Type" "text/html" "Connection" "close"         

    Cheers, Kai