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Multiple computers inside the network run various OSes, and connect through Wi-Fi or Physical connection. My desktop runs Ubuntu 11.04 64 bit, and has consistently slow or failing NSLookups.

I bought a new network card, which didn't help. Bought a new Wi-Fi adapter, didn't help. Installed Windows, didn't help. The only alternative is to change the motherboard.

I logged two parameters using a shell script over the course of two hours:

  • ping google.com
  • time nslookup google.com

Ping reports 13% packet loss, and Nslookup times out constantly, and has a rough average of 13 seconds, while it also resolves instantly at times.

I'm not sure what to do. I don't want to replace the motherboard, is there any other alternative?

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What are you name servers ? –  Iain Sep 10 '11 at 11:37
    
I changed it to openDNS and Google DNS, and it still didn't seem to help. I even modified the dhclient script to forcibly override the DHCP supplied nameservers. –  skyronic Sep 10 '11 at 17:48

2 Answers 2

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First identify why it is slow. Its unclear from your description where the issue is.

Steps I would take run "strace dig google.co.uk" take a look at the system calls and ths time between them where is the time spent ?

If its the network what does ping show to your gateway/router ? Packet loss and rtt.

check the settings of your router there may be clever anti virus / malware software intercepting dns traffic.

You could also try hping3 and test different types of traffic do you see the same delays on port 80 tcp as you do 53 udp ?

Untill you get it sorted maybe even after consider running a caching dns server on your ubuntu box it may help make it berable.

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Thank you for your suggestions. Unfortunately none of them seemed to really show where packet loss are. Fortunately, I ran a caching DNS Server and things seem to work great, for now atleast! –  skyronic Sep 11 '11 at 3:33

Try running

mtr 8.8.8.8

this combines the functionality of traceroute and ping. It may help you figure out where the packets are being dropped.

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hmm, right now it seems to be working fine, but when it fails, the traceroute fails right at localhost. –  skyronic Sep 11 '11 at 3:29

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