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ITGem's avatar
ITGem
Icon for Altocumulus rankAltocumulus
Dec 04, 2017

GDNS GTM DNS iRule Response Round Robin A Records for SVIP Databases

GTM/LTM version 11.3.0 HF 10.

Does anyone have an GTM DNS iRule that can be used to return three A records? I need a way to load balance databases between datacenters without changing their existing SVIP IP addresses. The LTMs have no connections (VLANs, self IPs) to the databases. We don't want to pass this traffic through our LTMs. Here is what I have tried to get working: I have not been able to get this to return three IP addresses: when DNS_REQUEST { Log query details log local0. "[DNS::question name]: [DNS::question name],\ [DNS::question class]: [DNS::question class], [DNS::question type]: [DNS::question type]"

if { [IP::addr [IP::remote_addr] equals x.x.x.x/x] } { host 10.x.x.x } else { host 10.x.x.x 10.x.x.x 10.x.x.x } }

I found this on this site but have not been able to get the DNS::answer insert to work:

Send one or more IP addresses for a response to an A query Use on an LTM virtual server with a DNS profile enabled

when DNS_REQUEST { Log query details log local0. "[DNS::question name]: [DNS::question name],\ [DNS::question class]: [DNS::question class], [DNS::question type]: [DNS::question type]"

 Generate an answer with two A records
DNS::answer insert "[DNS::question name]. 111 [DNS::question class] [DNS::question type] 10.x.x.x"
DNS::answer insert "[DNS::question name]. 111 [DNS::question class] [DNS::question type] 10.x.x.x"

 Stop further processing of the query after this iRule and send the answer to the client
DNS::return

}

Any help would be greatly appreciated.

application delivery
BIG-IP DNS
iRules
  • scottn4milesto1's avatar
    scottn4milesto1
    Icon for Nimbostratus rankNimbostratus
    Dec 04, 2017

    Give this a try;

    when DNS_REQUEST {
if { [IP::addr [IP::remote_addr] equals x.x.x.x/x] } { 
    host 10.x.x.x 
} 
    else { 
     Generate an answer with three A records
    DNS::answer insert "[DNS::question name]. 111 [DNS::question class] [DNS::question type] 1.1.1.1"
    DNS::answer insert "[DNS::question name]. 111 [DNS::question class] [DNS::question type] 1.1.1.2"
    DNS::answer insert "[DNS::question name]. 111 [DNS::question class] [DNS::question type] 1.1.1.3"
}
DNS::return
}
  • ITGem's avatar
    ITGem
    Icon for Altocumulus rankAltocumulus
    Dec 04, 2017

    Thanks Scott.

     

    I get errors: line 5: [undefined procedure: DNS::answer] [DNS::answer insert "[DNS::question name]. 111 [DNS::question class] [DNS::question type] 1.1.1.1"] line 9: [undefined procedure: DNS::return] [DNS::return]

     

    I know I need to change the IP address but what procedure is it referring to?

     

    Thanks

     

  • scottn4milesto1's avatar
    scottn4milesto1
    Icon for Nimbostratus rankNimbostratus
    Dec 04, 2017

    If you do not have LTM licensed on the unit, you would be best configuring this with 'topology' LB.

     

    Create two pool:

     

    1) with the single IP

     

    2) with the three IPs

     

    Then use Topology to send traffic to pool one if the subnet matches, 0.0.0.0/0 send to pool 2.

     

  • ITGem's avatar
    ITGem
    Icon for Altocumulus rankAltocumulus
    Dec 05, 2017

    I like......but that means I would have to create VIPs on the LTM for the pools? That's a lot of VIPs since we have approximately 40 databases. ???? I mean I will do it if I have to but Have you ever had success modifying zone runner? I was able to create the record in zonerunner but zonerunner sometimes stops working when I query the record because of a bug limiting the FQDN to less than 25 characters. Again, any help is much appreciated.

     

  • ITGem's avatar
    ITGem
    Icon for Altocumulus rankAltocumulus
    Dec 05, 2017

    Here is the zonerunner record. IPs and names have been changed of course.

     

    [jdoeitexp@computer ~]$ dig gtmtest01.globalqa.testltm.testgtm.com

     

    ; <<>> DiG 9.3.6-P1-RedHat-9.3.6-25.P1.el5_11.2 <<>> gtmtest01.globalqa.testltm.testgtm.com ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26177 ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 0

     

    ;; QUESTION SECTION: ;gtmtest01.globalqa.testltm.testgtm.com. IN A

     

    ;; ANSWER SECTION: gtmtest01.globalqa.testltm.testgtm.com. 0 IN A 10.x.x.x gtmtest01.globalqa.testltm.testgtm.com. 0 IN A 10.x.x.x gtmtest01.globalqa.testltm.testgtm.com. 0 IN A 10.x.x.x

     

    ;; Query time: 3 msec ;; SERVER: 172.x.x.x53(172.x.x.x) ;; WHEN: Mon Dec 4 19:41:23 2017 ;; MSG SIZE rcvd: 102

     

  • scottn4milesto1's avatar
    scottn4milesto1
    Icon for Nimbostratus rankNimbostratus
    Dec 05, 2017

    You could create the servers/virtual servers on the GTM as generic hosts if they are not currently behind an LTM.

     

  • ITGem's avatar
    ITGem
    Icon for Altocumulus rankAltocumulus
    Dec 05, 2017

    Hello Scott.

     

    I believe I need an LTM license to do this. Under local traffic I don't have the virtual servers menu. I only see the option to add LTM VIPs as pool members in my GTM. Please clarify.

     

  • ITGem's avatar
    ITGem
    Icon for Altocumulus rankAltocumulus
    Dec 07, 2017

    Hello Scott.

     

    Regarding my previous comment to you above (see below), please clarify that I need an LTM license to enable this procedure in the GTM.

     

    I get errors: line 5: [undefined procedure: DNS::answer] [DNS::answer insert "[DNS::question name]. 111 [DNS::question class] [DNS::question type] 1.1.1.1"] line 9: [undefined procedure: DNS::return] [DNS::return]

     

    Also, do you know of any documentation you can point me to?

     

    Thanks very much.

     

    BTW. You have been very helpful and I have several options to consider.