Big issue with Telecom DNS caches for a web developer

Forums › Spark New Zealand (including Skinny and BigPipe) › Big issue with Telecom DNS caches for a web developer

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timsimpson

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#425018 7-Jan-2011 17:22

Hi All

xtra do honor TTLs but like all ISP's they set a minimum - I belive that for terminator and alien this is 300s

For DNSC1.xtra.co.nz, DNSC2.xtra.co.nz, ns1.xtra.co.nz and ns2.xtra.co.nz the minimum is 900s

Anyone from telecom please correct me if I'm wrong :D

As a general note - if you're getting these kind of timeouts and posting them here, can you take the time to do a couple of NS lookups and see exactly which DNS servers you are using. This can help people who read this quite a lot in solving the issues.

BlakJak

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#425024 7-Jan-2011 17:50

Um.. Hi Tim.. Did you spy this from a Telecom employee?

"The Telecom DNS caches do honor TTL, so lowering the TTL will work on our network."

It appeared earlier in this thread.

{citation needed} please... ??

No signature to see here, move along...

BlakJak

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#425036 7-Jan-2011 18:57

ptinson:
ptinson:
I think from memory negative cache is 1 hr but i will check later.

Its 3 hours.

Hangon. the SOA record for a DNS zone includes the negative-record TTL.

Are you suggesting Xtra/Telecom overrides this with their own figure (3 hrs) ?

http://www.netadmintools.com/art232.html for ref.

No signature to see here, move along...

ptinson

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#425101 8-Jan-2011 07:27

timsimpson: Hi All

xtra do honor TTLs but like all ISP's they set a minimum - I belive that for terminator and alien this is 300s

For DNSC1.xtra.co.nz, DNSC2.xtra.co.nz, ns1.xtra.co.nz and ns2.xtra.co.nz the minimum is 900s

Anyone from telecom please correct me if I'm wrong :D

As a general note - if you're getting these kind of timeouts and posting them here, can you take the time to do a couple of NS lookups and see exactly which DNS servers you are using. This can help people who read this quite a lot in solving the issues.

Alien and Terminator recursive servers are the same ones as dnsc1 & 2 and they have no defined minimum cache time, The have a maximum that is currently 7 days though.

ns1 & 2 also have no defined minimum, but have the same 7 day max.

Paul

meat popsicle

ptinson

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#425106 8-Jan-2011 08:09

BlakJak:
ptinson:
ptinson:
I think from memory negative cache is 1 hr but i will check later.

Its 3 hours.

Hangon. the SOA record for a DNS zone includes the negative-record TTL.

Are you suggesting Xtra/Telecom overrides this with their own figure (3 hrs) ?

http://www.netadmintools.com/art232.html for ref.

Sorry meant to reply all in one post but got distracted.

We have a max ncache ttl of 3 hrs so if your negative TTL in the SOA is larger than this we will ignore that yes. Sorry not a default ncache TTL of 3 hours.

I would be happy to hear any suggestions to a different value.

Paul

meat popsicle

BlakJak

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#425109 8-Jan-2011 08:23

Surprised you don't just honour the value in zones as published...?

No signature to see here, move along...

Quic Broadband

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ptinson

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#425133 8-Jan-2011 10:13

Experience and a fair amount of testing has shown 3hrs to be a good value for ncache MAX TTL.

Also rfc2308 points this out and why leaving it to be whatever is set in the SOA could be problematic.

the important thing to note is as far as i know we don't monkey with the MIN TTL, even if we may have been tempted to for some domains.

For positive responses a MAX TTL of 7 days is quite some time given most TLD's have a TTL of 2 days, which is still quite long.

meat popsicle

BlakJak

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#425237 8-Jan-2011 16:39

Yeah, I would not see any point in a TTL >2 days - nor a negative TTL of more than an hour, to be honest...

Thanks for popping up here Paul with solid info and explanations.

No signature to see here, move along...

timsimpson

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#425357 9-Jan-2011 01:17

BlakJak: Um.. Hi Tim.. Did you spy this from a Telecom employee?

"The Telecom DNS caches do honor TTL, so lowering the TTL will work on our network."

It appeared earlier in this thread.

{citation needed} please... ??

Nah I just missed seeing it. Damn Hunan failings ;)

ptinson

677 posts

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#425393 9-Jan-2011 10:03

BlakJak: Yeah, I would not see any point in a TTL >2 days - nor a negative TTL of more than an hour, to be honest...

Thanks for popping up here Paul with solid info and explanations.

No Problem, all part of being friendly and helpful...

Paul

meat popsicle

snnet

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#425883 10-Jan-2011 19:24

ptinson:
BlakJak: Yeah, I would not see any point in a TTL >2 days - nor a negative TTL of more than an hour, to be honest...

Thanks for popping up here Paul with solid info and explanations.

No Problem, all part of being friendly and helpful...

Paul

Paul, are you still offering to switch off caching for static IP users? Thought I'd ask before PMing you :)

Dyson

Shop now for Dyson appliances (affiliate link).

ptinson

677 posts

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#425909 10-Jan-2011 21:17

Yes.
You need to send me your static IP and i can arrange to have it bypassed

Paul

meat popsicle

da5id

550 posts

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#426546 12-Jan-2011 15:19

I admit to having no idea about this network stuff or VPN etc (I had to look it up).

I notice that LogMeIn has a VPN networking service called Hamachi² that has a free version for up to 16 clients.

It this useful? pertinent? How does it work?

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