asked on

DNS servers not caching certain DNS records

Hello,

We have 2 x 2008R2 DCs in a site A which are caching some DNS records but not caching other DNS records. This seems to be affecting DNS performance.

We have 2 x 2008R2 DCs in site B which are caching all records as expected.

All servers are using Root Hints.

Example:

Site A DCs: ft.com in DNS cache shows 4 NS records

ns1.p23.dynect.com
ns2.p23.dynect.com
ns3.p23.dynect.com
ns4.p23.dynect.com

When I do:

NSLookup www.ft.com.

I get this response:

Non-authoritative answer:
Name: e.global-ssl.fastly.net
Address: 185.31.17.230
Aliases: www.ft.com

But the record for www.ft.com is not cached.

Site A DCs: ft.com in DNS cache shows 4 NS records

ns1.p23.dynect.com
ns2.p23.dynect.com
ns3.p23.dynect.com
ns4.p23.dynect.com

When I do:

NSLookup www.ft.com.

I get this response:

Non-authoritative answer:
Name: e.global-ssl.fastly.net
Address: 185.31.17.230
Aliases: www.ft.com

But the record for www.ft.com is not cached.

In SIte B, the same nslookup command results in the caching of:

ns1.p23.dynect.com
ns2.p23.dynect.com
ns3.p23.dynect.com
ns4.p23.dynect.com

and the caching of CNAME for www => e.global-ssl.fastly.net

Has anyone ever seen this behaviour?

Any idea why DC in one site is caching the www record and DC in other site is not?

Thanks.

Dan McFadden

Are you sure the DNS services are configured the same in both sites?

I resolve the nslookup to the following:

C:\>nslookup www.ft.com
Server:  abc.xyz.123
Address:  1.2.3.4

Non-authoritative answer:
Name:    e.global-ssl.fastly.net
Address:  185.31.17.230
Aliases:  www.ft.com

Open in new window

I cannot resolve the FQDNs for: nsX.p23.dynect.com

I would check your forwarder configuration on the DCs in site A and compare them to site B's config.

Dan

W S

ASKER

Thanks Dan.

Typo in the original question (apologies), results are:

ns1.p23.dynect.net
ns2.p23.dynect.net
ns3.p23.dynect.net
ns4.p23.dynect.net

Dan McFadden

How about your forwarder configuration? There is no relation between fastly.net and dynect.net that I can find.

Again, I believe you have a configuration difference between your 2 sites. fastly.net is a global CDN and dynect is a managed DNS provider. faslty is based in San Francisco, CA, USA and DynEct is in Australia.

1. How is TCP/IP configured on the DCs at each site?
1a. what are the DC's DNS configuration?
2. What (if any) is the DNS forwarding configuration on the DCs at each site?
2a. Are you sure that all DCs in all sites are configured the same way?
3. Are there any proxies in place that could redirect outbound DNS queries?

Dan

W S

ASKER

Hello Dan,

Thanks for the input.

We are testing some alternate configurations.

I'll get back with results.

Thanks.

This question needs an answer!

Become an EE member today

7 DAY FREE TRIAL

Members can start a 7-Day Free trial then enjoy unlimited access to the platform.

View membership options

Learn why we charge membership fees

We get it - no one likes a content blocker. Take one extra minute and find out why we block content.