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N_67263's avatar
N_67263
Icon for Nimbostratus rankNimbostratus
Aug 28, 2017

iRule which strips of the domain name and replaces that with another domain name.

Team, Can anyone help me with an iRule which strips of the domain name and does a DNS query with some other domain name? e.g. The F5 intercepts a request on "xyz.externaldomain.com". F5 strips of the...
application delivery
iRules
  • Yann_Desmarest_'s avatar
    Yann_Desmarest_
    Aug 28, 2017

    Hi,

    Maybe the following irule may help you :

    when HTTP_REQUEST {
    if { [HTTP::host] contains "xyz.externaldomain.com" } {
        HTTP::header replace Host "xyz.internaldomain.com"
    }
}

    You may also use 

    string map
    command to make the replacement more dynamic

Kai_Wilke's avatar
Kai_Wilke
Icon for MVP rankMVP
Aug 29, 2017

Hi N,

 

please don't open multiple question for the same topic. It doesn't make sense if independent people spend their valuable time to answer your redundant questions over and over...

 

https://devcentral.f5.com/questions/understanding-the-host-in-the-http-request-55264

 

https://devcentral.f5.com/questions/irule-which-strips-of-the-domain-name-and-replaces-that-with-another-domain-name-55273

 

https://devcentral.f5.com/questions/node-autoselection-using-dns-55263

 

Note: I've already told you to add some error handles to your iRule, to become able to indentify where it breaks. In addition to that I've linked K12225 [click me] to make sure the DNS on your F5 allows recursive DNS queries. I've also speak out the recommendation to setup a DNS Virtual Server to become able to query a pool of redundant DNS servers.

 

Well, based on your latest requirements (added external / internal DNS domain conversation) the resulting iRule code would look like that...

 

when HTTP_REQUEST { 
    if { [HTTP::host] eq "xyz.externaldomain.com" } then {
        set ips [lindex [RESOLV::lookup -a "[getfield [HTTP::host] "." 1].internaldomain.com"] 0]
        log local0.debug "Debug: Resolved address for \"[getfield [HTTP::host] "." 1].internaldomain.com\" = \"$ips\"" 
        if { $ips ne "" } then {
            node $ips [TCP::local_port]
        } else {
            HTTP::respond 504 content "Bad Request - unknown HOST value"
        }
    } else {
        HTTP::respond 504 content "Bad Request - wrong HOST value"
    }
}

Cheers, Kai