X-Forward-Proto for HTTP version identifier(1.0/2)

You might be able to use the HTTP2::active command in the iRule to determine if the client connected using HTTP/2 or not. For example:

when HTTP_REQUEST {
  if { [HTTP2::active] } {
    log local0. "Request from HTTP/2 client"
  } else {
    log local0. "Request from HTTP client"
  }
}

You can find more information on HTTP2::active here. You can also check out the other HTTP2 commands here.

 I guess this only logs in LTM local. Is there any way we can insert in header like X-Forward-Proto ? Where backend owner can distinguish the connections b/w HTTP/1 or HTTP/2 ??

Sure, just change the log commands to anything of your choice, such as inserting an HTTP header. The iRule I provided was simply an example of how you might use the HTTP2::active command to distinguish between HTTP and HTTP/2.

 I came up with below iRule. What do you think on this ?

ltm rule rule-http-protocol-version {

  when HTTP_REQUEST {

 if { [HTTP2::active] } {

  HTTP::header insert Version HTTP/2

 } else {

  HTTP::header insert Version HTTP

 }

}

 Thank you very much for your help on this. Its worked as expected.