Forum Discussion

Alejandro_Reyes's avatar
Alejandro_Reyes
Icon for Nimbostratus rankNimbostratus
Mar 10, 2011

fast DNS with two answers

Hi

 

 

Searching in the irule wiki home, i found a code called fast_dns. This irule can be applied to reply querys of an a particular host (FQDN) to client directly from the F5. http://devcentral.f5.com/wiki/default.aspx/iRules/fast_DNS.html

 

 

I configured this for a client, but in their particular case, it need that the answer for a host (FQDN) will be a couple of ip address. I tried to modify this irule but until this moment i can´t do it work .

 

 

Is there a way to configure it?

 

 

thanks in advance

 

 

application delivery
dev
devops
iRules
  • Nat_Thirasuttakorn's avatar
    Nat_Thirasuttakorn
    Icon for Employee rankEmployee
    Mar 10, 2011
    Hi Erneri,

     

     

    try the new version...

     

    http://devcentral.f5.com/wiki/default.aspx/iRules/fast_DNS_2.html

     

     

    what you need is customize static::domain and static::answer_string variable in RULE_INIT

     

     

    Nat
  • Alejandro_Reyes's avatar
    Alejandro_Reyes
    Icon for Nimbostratus rankNimbostratus
    Mar 10, 2011
    Nat,

     

     

    Thanks for your quick answer. I'll try to customize this irule with our custumer. Actually we resolved this with the next code

     

     

     

     

    when RULE_INIT {

     

    Header generation (in hexadecimal)

     

    qr(1) opcode(0000) AA(1) TC(0) RD(1) RA(1) Z(000) RCODE(0000)

     

    set ::header1 "8580"

     

    set ::header2 "8580"

     

    1 question, 1 answer, 0 NS, 0 Addition

     

    set ::header1 "${::header1}0001000200000000"

     

    set ::header2 "${::header2}0001000100000000"

     

    Name = www.f5.com

     

    set ::answer1 ""

     

    set ::answer2 ""

     

     

    Type = A

     

    set ::answer1 "${::answer1}0001"

     

    set ::answer2 "${::answer2}0001"

     

    Class = IN

     

    set ::answer1 "${::answer1}0001"

     

    set ::answer2 "${::answer2}0001"

     

    TTL = 1 day

     

    set ::answer1 "${::answer1}00015180"

     

    set ::answer2 "${::answer2}00015180"

     

    Data length = 4

     

    set ::answer1 "${::answer1}0004"

     

    set ::answer2 "${::answer2}0004"

     

    Address = 3.3.3.3

     

    set ::answer1 "${::answer1}01010101"

     

    set ::answer2 "${::answer2}02020202"

     

    log local0. "match init"

     

    }

     

    when CLIENT_DATA {

     

    binary scan [UDP::payload] H4@12A*@12H* id dname question

     

    set dname [string tolower [getfield $dname \x00 1 ] ]

     

    switch -glob $dname {

     

    "\x03www\x02f5\x03com" {

     

    set payload [binary format H* ${id}${::header1}${question}${::answer1}${::answer2} ]

     

    drop

     

    UDP::respond $payload

     

    UDP::payload replace 0 0 $payload

     

    }

     

    default {

     

    log local0. "does not match"

     

    }

     

    }

     

    }

     

     

     

     

    As soon as we test it, we´ll post our results

     

     

     

    Thanks again

     

     

    Regards

     

    erneri
  • hooleylist's avatar
    hooleylist
    Icon for Cirrostratus rankCirrostratus
    Mar 10, 2011
    Hi erneri,

     

     

    Are you on 10.x? If so, you can make the iRule CMP compatible by changing the global variables ($::header1, etc) to statics ($static::header1, etc).

     

     

    http://devcentral.f5.com/wiki/default.aspx/iRules/CMPCompatibility.html

     

     

    Aaron