Reply
Accepted Solution

DNS Resolution mechanism

TheFlyingFox
Techie
Posts: 4
363     1

Hi guys,

 

I have configured one A Record with 3 different IPs,

 

www.company.com 10.10.10.1

www.company.com 10.10.20.1

www.company.com 10.10.30.1

 

I need to know what is the algorithm used by NIOS when a user is resolving www.company.com :

 

will it be  balanced ?

10.10.10.1     33%

10.10.20.1     33%

10.10.30.1     33%

 

is it Random ?

 

In My case DNS server returns the same IP 80% of the time, which is the first IP entered.

 

Thank You

Re: DNS Resolution mechanism

devnull09
Techie
Posts: 6
363     1

You can't configure one A record with 3 different IPs. Each A record has exactly one IP.

 

So you either configured:

 

a) 3 A records, each with the same name but with different IPs

 

or

 

b) one host record containing 3 IPs

 

However, for both a) and b) the default behaviour is round-robin, so distribution should be 1/3 for each of the three IPs.

 

Are you 100% sure there were no other queries to the server in between your queries ? The round-robin distribution is a total distribution across ALL queries received on the DNS server. It is not a per-client round-robin distribution.

So for proper testing/verification you'll have to ensure you are the only client sending queries to that DNS server at that time.

 

You can also setup different distribution/ordering schemes as per:

 

https://docs.infoblox.com/display/nios84/Enabling+the+Configuration+of+RRset+Orders

 

 

 

 

 

 

 

Re: DNS Resolution mechanism

TheFlyingFox
Techie
Posts: 4
363     1

Hi @evnull09 

 

Yes I have 3 A Records same name and different IPs.

 

The document talks only about host record "Enable setting RRset order for hosts with multiple addresses

Does it apply to simple A Records ?

 

Do I have to Add host with 3 IPs instead of 3 A Records with same name and multipe IPs ?

 

Thank You

Highlighted

Re: DNS Resolution mechanism

devnull09
Techie
Posts: 6
363     1

Hi,

 

that setting probably only applies to Host records. Not sure what the algorithm is if you setup 3 A records for the same label, like you did.

 

I did a quick test and 3 individial A records as well as a host record with three IPs showed the same behaviour. The answers were always round-robin so for 9 queries sent I got 3 replies with each of the three IPs on top of the list, so exactly the expected result of 1/3.

 

When you are testing, are you actually sending your test queries to the authoritative DNS server for the zone ? Or are you using a local cache/resolver ? If you are using a local cache then that cache might use another distribution scheme, so you should make sure to test against the auth server directly.

 

Showing results for 
Search instead for 
Do you mean 

Recommended for You