Round robin load distribution among servers does not work properly

[Mallappa Pallakke]

Hi,

 I tried with 9.5.1.P2, but still I am not getting the expected round
robin results:

 Please see below my named.conf and zone file:

named.conf:
=========
options {
       directory "/var/named";

       // Uncommenting this might help if you have to go through a
       // firewall and things are not working out.  But you probably
       // need to talk to your firewall admin.

       //query-source port 53;

rrset-order {
        order cyclic;};    // fixed, random, cyclic
};

zone "mycompany.com" {
       type master;
//        notify no;
       file "db.mycompany.com";

       allow-update { any; };
//      allow-update { 127.0.0.1; };
notify yes;
};


db.mycompany.com:
===============
$ORIGIN .
$TTL 0  ;
mycompany.com           IN SOA  www.mycompany.com. hostmaster.mycompany.com. (
                               199813404  ; serial
                               1          ; refresh (1 second)
                               1          ; retry (1 second)
                               1          ; expire (1 second)
                               1          ; minimum (1 second)
                               )
                       NS      www.mycompany.com.
$ORIGIN mycompany.com.
localhost               A       127.0.0.1
$TTL 0  ;
www                     A       10.10.68.1
                       A       10.10.68.2
                       A       10.10.68.3
                       A       10.10.68.4


I always get following answers repeatedly. Not getting 10.10.68.2 and
10.10.68.3 as top records in response messages:
=================================================
atcafs-n4s1:/kwlogs/msp# dig www.mycompany.com

; <<>> DiG 9.3.2 <<>> www.mycompany.com
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 13961
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;www.mycompany.com.             IN      A

;; ANSWER SECTION:
www.mycompany.com.      0       IN      A       10.10.68.4
www.mycompany.com.      0       IN      A       10.10.68.1
www.mycompany.com.      0       IN      A       10.10.68.2
www.mycompany.com.      0       IN      A       10.10.68.3

;; AUTHORITY SECTION:
mycompany.com.          0       IN      NS      www.mycompany.com.

;; Query time: 1 msec
;; SERVER: 10.10.68.1#53(10.10.68.1)
;; WHEN: Sun Apr  6 00:21:07 2008
;; MSG SIZE  rcvd: 113


=================================================

atcafs-n4s1:/kwlogs/msp# dig www.mycompany.com

; <<>> DiG 9.3.2 <<>> www.mycompany.com
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 65208
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;www.mycompany.com.             IN      A

;; ANSWER SECTION:
www.mycompany.com.      0       IN      A       10.10.68.2
www.mycompany.com.      0       IN      A       10.10.68.3
www.mycompany.com.      0       IN      A       10.10.68.4
www.mycompany.com.      0       IN      A       10.10.68.1

;; AUTHORITY SECTION:
mycompany.com.          0       IN      NS      www.mycompany.com.

;; Query time: 1 msec
;; SERVER: 10.10.68.1#53(10.10.68.1)
;; WHEN: Sun Apr  6 00:21:09 2008
;; MSG SIZE  rcvd: 113

==================================================


Please let me know anything is missing.

Regards,
Mallappa Pallakke


On Sun, Apr 5, 2009 at 8:55 AM, Kirk <bind at kirkb.net> wrote:
> Mallappa Pallakke wrote:
>>
>> Hi,
>>
>>    I was trying to do load balancing of client request among
>> configured servers using internal DNS server, I get proper load
>> balaning (DNS response with top most IP address going with proper
>> round robin fashio) for odd number of IP addresses. But it does not
>> give same bevior for even number of IP addresses.
>>
>> For example:
>>
>>  If I have configured x.y.z.1, x.y.z.2, x.y.z.3, I get following
>> combinations in dig response:
>>
>>  x.y.z.1
>>  x.y.z.2
>>  x.y.z.3
>>
>>  x.y.z.2
>>  x.y.z.3
>>  x.y.z.1
>>
>>  x.y.z.3
>>  x.y.z.1
>>  x.y.z.2
>>
>> And this repeats, giving round robin distribution.
>>
>> However, if I add one more IP address to the zone list (x.y.z.4), I
>> get only following combinations:
>>
>> x.y.z.1
>> x.y.z.2
>> x.y.z.3
>> x.y.z.4
>>
>> and
>>
>> x.y.z.3
>> x.y.z.4
>> x.y.z.1
>> x.y.z.2
>>
>> It gets repeated. I will never get x.y.z.2 and x.y.z.4 as top entries
>> in this response.
>>
>> Can anybody tell me why this limitation and is there any sollution to
>> resove this problem?
>>
>> Thanks in advance.
>>
>> Mallappa
>
>
> Not sure what version of BIND you are using, but here I am using 9.5.1-P2.
>  I just loaded a zone with 10 www records and different IP's and they are
> handed out round robin just fine.
>
> The idea of using DNS for load balancing has been brought up here so many
> times its hard to count.  The answer is always the same. DNS was *never*
> meant to provide this functionality.  Spend the big bucks and get a device
> meant to do *load balancing*.
>
> Search the archive for previous threads on this subject.
> http://marc.info/?l=bind9-users&w=2&r=1&s=load+balancing&q=b
>