DNS Servers changing very often - performance implications - IS backbone

[Aquadyne]

Hey everyone,

So I am curious about something I noticed over the last few months.

The DNS servers that are dynamically assigned to my IP by the ISP seems to change very very often - even within a session.

Why would it be that the ISP would need to change them so often?
Given the recent spate of terrible speeds that seem to be somewhat random and not across the board, I was wondering if there is some correlation between these factors.

I have to say that I only noticed this on the IS backbone (Afrihost & Openweb).

As a snapshot quick survey can those of you that feel inclined perhaps post the following here.

The primary assigned DNS
The secondary assigned DNS
Default Gateway
The ISP & backbone if known
Line Speed & Package
Your current perceived performance

I know that many of you override the DNS settings and configure your own static ones, but the router will still show you the ISP assigned ones.

Today:

Primary DNS: 168.210.2.2
Secondary DNS: 196.14.239.2
Default Gateway : 196.215.154.129
Afrihost / IS
4M / 4M Uncapped
Below par performance - but slightly better

I might have it all completely wrong, but I am curious by nature and the randomness is maybe not random at all.

Maybe there is a pattern

 

[guest2013-1]

The assigned IP addresses by the ISP can't change within a session unless your connection actually drops and you have to reconnect again.

Setting static IP addresses for your DNS can be done on the router (what you were describing I would imagine it's on your connection TO the router)

Even though this is on the IS backbone, you didn't mention which ISP we're dealing with here or what kind of router you have or what your SNR/Line Attenuation is. 99% of the times it's not because of a DNS server or gateway IP's with the same IP as the secondary DNS, but your physical line (or just a really crap ISP)

Give MWEBGuy a PM and ask for a trial account, check if the same thing happens and if your speed is still crap. If not, ISP. If yes, line.

 

[Aquadyne]

I must have been smoking crack... Just noticed that I took down the details from last night incorrectly.

My point still stands though, I'd like to see the pattern and see the variables.

Too often when I was with Openweb, I would just be given a new logon to resolve an issue. No problems were actually addressed or fixed.
Sure, the problem went away - but only temporarily.

 

[Tinuva]

The assigned IP addresses by the ISP can't change within a session unless your connection actually drops and you have to reconnect again.

Setting static IP addresses for your DNS can be done on the router (what you were describing I would imagine it's on your connection TO the router)

Even though this is on the IS backbone, you didn't mention which ISP we're dealing with here or what kind of router you have or what your SNR/Line Attenuation is. 99% of the times it's not because of a DNS server or gateway IP's with the same IP as the secondary DNS, but your physical line (or just a really crap ISP)

Give MWEBGuy a PM and ask for a trial account, check if the same thing happens and if your speed is still crap. If not, ISP. If yes, line.

He has actually noted his ISP is Afrihost/IS. I saw that in his post before you replied.

I must have been smoking crack... Just noticed that I took down the details from last night incorrectly.

My point still stands though, I'd like to see the pattern and see the variables.

Too often when I was with Openweb, I would just be given a new logon to resolve an issue. No problems were actually addressed or fixed.
Sure, the problem went away - but only temporarily.

Openweb and Afrihost are just resellers. They do not always follow up on such technical issues with their supplier. That said, it is important to actually have an ISP that will follow up on these problems, if there really are problems with a specific DNS server, there should be a pattern of users experiencing the problem, which should make it noticable to the ISP that there is a serious problem that needs to be attended to.

Alternatively, you could always try using opendns, googledns or some of the other ISP servers that are open.

Here is a list:
8.8.8.8 - London - GoogleDNS
8.8.4.4 - London - GoogleDNS
208.67.222.222 - London - OpenDNS
208.67.220.220 - London - OpenDNS
196.41.0.10 - JHB - Datapro/VOX
196.7.142.132 - CPT - MTN-Business
196.2.45.101 - JHB - M-Web
196.2.53.140 - CPT/JHB - M-Web
196.2.48.227 - CPT - M-Web
196.207.32.69 - JHB - Vodacom
196.220.59.188 - CPT - WA
196.220.59.189 - CPT - WA

 

[guest2013-1]

He has actually noted his ISP is Afrihost/IS. I saw that in his post before you replied.

Had to re-read it again, I skipped that sentence as it looked like a repeat of his topic again. My bad.

I still say that his physical line might be acting up

 

[Aquadyne]

Again, the purpose of this thread is not purely to fix a problem, but to gather information that might shed light on an ongoing problem.

I am not currently looking for advice on changing my settings or indeed service provider.

Does everyone from a particular ISP use the same settings for DNS & Gateway servers?
Does it vary between different accounts?
How common are these settings to the backbone provider?
Does it ever change in the short-term?
What are the real-world implications relating to performance perception.?

As I said, gathering information at this stage..

 

[noswal]

You can download a very small program here http://www.grc.com/dns/benchmark.htm and run tests and find the fastest dns for you. Try it several times over a day to get a best average.

FWIW im with iburst, but with above I dont use their dns but mtn as they are faster when i last tested.

 

[ranger]

Again, the purpose of this thread is not purely to fix a problem, but to gather information that might shed light on an ongoing problem.

I am not currently looking for advice on changing my settings or indeed service provider.

Does everyone from a particular ISP use the same settings for DNS

Not necessarily.

& Gateway servers?

No. Your gateway is location- and "backbone"-dependant

Does it vary between different accounts?

Different accounts from the same ISP? Typically not, but it can.

How common are these settings to the backbone provider?

Gateway, same for users on the same backbone in the same location. DNS? Depends on the "backbone".

Does it ever change in the short-term?

Not shorter than your PPPoE session.

What are the real-world implications relating to performance perception.?

Really, really depends. You haven't provided much information on what is slow. For example, slow DNS isn't going to affect how fast a youtube video downloads, but using incorrect (e.g. overseas) DNS servers will (as it prevents CDNs from working the way they should).

 

[Aquadyne]

Thanks Ranger for that...

I got into the habit of using 8.8.8.8 and 8.8.4.4 as my dns servers by overriding the allocated ones on my router configuration.
This was done after having several ongoing issues at one stage with dns not resolving with the isp allocated ones.
I also thought that the isp has a method of control over my session and performance if they control the dns and subsequent routing.

It became habit, but I still sometimes experience dns not resolved issues, where I have to restart my router to get going again with the exception of active torrents that seem to perform very well through distributed trackers.

Thanks for your answer, I appreciate it.

 

[ranger]

I also thought that the isp has a method of control over my session and performance if they control the dns and subsequent routing.

The ISP can't control routing through DNS, but CDNs often use DNS-based server-selection.

All ISPs have some kind of shaping, congestion control, traffic optimisation or content acceleration platforms, which are there to provide a better service at lower cost. Using different DNS servers won't affect these.

Unfortunately, these optimisation platforms (e.g. any transparent proxy) can theoretically impact DNS (or access to sites) to some extent, but the best thing to do in this case is report the problem.

It became habit, but I still sometimes experience dns not resolved issues, where I have to restart my router to get going again with the exception of active torrents that seem to perform very well through distributed trackers.

If you are having problems that are resolved by restarting your router, I would suspect the router. Next time you have problems, it would be prudent to put the DNS IPs on the router on your PC, and see if that shows an improvement. If so, it is the DNS software on your router causing the problems.