Resolving DNS takes much time

[Pravin Raj Kanagaraj]

Hey all,

We have Cisco ASA connected to l3, l2 switches, Radware.

We have DHCP, DNS enabled from Active Directory.

From past one week, many websites don't respond to and after refreshing it instantly it loads but it takes time.

Also while resolving DNS it takes so much time.

Troubleshooting I performed :

I thought DNS could be the problem so I changed DNS to 8.8.8.8 on my PC and all websites work fine. I escalated the issue to server engineer and he states it is a network issue.

Waiting for your valuable comments. I have attached the network diagram for your info.

Thank you.

[Flavio Miranda]

Hi

Open up a powershell prompt in a Windows machine, copy and paste:

Measure-Command {Resolve-DnsName google.com -DnsOnly -Type A -Nohostsfile  -server x.x.x.x}

x.x.x.x is your server.

Then do it again using 8.8.8.8 as server.

This script will show you how long it takes to the DNS resolve the URL.

-If I helped you somehow, please, rate it as useful.-

[Pravin Raj Kanagaraj]

PowerShell throws me an error like resolve DNS-name is not recognised.

[paul driver]

Hello

What are the internal client using for DNS, Where are they being directed to for name resolution?

If you have multiple dns servers try specifying the secondary on as primary and test?

Are you using any web proxy?

res

Paul

[Pravin Raj Kanagaraj]

As I mentioned above we have windows server for DNS, I have tried with primary and secondary DNS still the same issue.

no web proxy has been used

[shaps]

if you run a packet capture against the DNS server and validate the repsonse times, if you can resolve using 8.8.8.8 without any issues then it is either something changed in the network or the DNS server is not happy. Where in the enviorment is the DNS server, it is a centralised setup

[Jon Marshall]

If the DNS server is in DMZ check the firewall rules as using 8.8.8.8 is inside to outside so different path. 

Jon