Add http header of Server IP address?

you should use HTTP::uri to rewrite client's http request uri,

iRules:

when HTTP_REQUEST {

switch -glob [string tolower [HTTP::uri]] { 

"/map1/admin*" -

"/map2/admin*" {

drop

log "Drop direct connection via admin URI"

}

"/map1/*" { 

HTTP::uri [string map {"map1" "land"} [HTTP::uri]]

pool http_pool member 10.1.20.11 80

}

"/map2/*" {

HTTP::uri [string map {"map2" "land"} [HTTP::uri]]

  pool http_pool member 10.1.20.12 80

}

"/land/*" {

  pool http_pool

}

default {

drop

  }

  }

}

[OT]

have you considered using a policy instead of an irule?

(I find them much more maintainable and even if they are less flexible they should do what you ask)