Jump to content

Welcome to Geeks to Go - Register now for FREE

Geeks To Go is a helpful hub, where thousands of volunteer geeks quickly serve friendly answers and support. Check out the forums and get free advice from the experts. Register now to gain access to all of our features, it's FREE and only takes one minute. Once registered and logged in, you will be able to create topics, post replies to existing threads, give reputation to your fellow members, get your own private messenger, post status updates, manage your profile and so much more.

Create Account How it Works
Photo

DNS Caching


  • Please log in to reply

#1
Ambiorix

Ambiorix

    New Member

  • Member
  • Pip
  • 1 posts
Hey everyone,

I've come here not with a problem but with a solution and I would like to know why this worked. This question is addressed to people who fully understand DNS.

The situation:

For some reason (here irrelevant), our DHCP server lost it's configuration, giving IP addresses to workstations that belong to servers. This caused an IP conflict. To find out which workstation got the server's IP, we deactivated the network card on the server, flushed the DNS cache on our computers, restarted DHCP en DNS service on the server and pinged the IP. It continued to return us the server's name.
So I configured my network card on my computer to use the DNS servers from Google. I figured that way, I wouldn't receive a cached response. It worked. But I don't fully understand why. The DNS servers from Google don't know the internal IP addresses, so I guess they referred to our own DNS server but why I received the correct answer (the computer name which got the server's IP) is a mystery to me.

Can someone enlighten me?
  • 0

Advertisements


#2
Hadronn

Hadronn

    Member

  • Member
  • PipPip
  • 21 posts
Interesting. Maybe server IPs work differently? Would like to know why you can get a reply from the ping while using DNS servers from Google too...

What protocol is your connected network in?
  • 0

#3
Neil Jones

Neil Jones

    Member 5k

  • Member
  • PipPipPipPipPipPipPipPip
  • 8,476 posts

For some reason (here irrelevant), our DHCP server lost it's configuration, giving IP addresses to workstations that belong to servers. This caused an IP conflict. To find out which workstation got the server's IP, we deactivated the network card on the server, flushed the DNS cache on our computers, restarted DHCP en DNS service on the server and pinged the IP. It continued to return us the server's name.
So I configured my network card on my computer to use the DNS servers from Google. I figured that way, I wouldn't receive a cached response. It worked. But I don't fully understand why. The DNS servers from Google don't know the internal IP addresses, so I guess they referred to our own DNS server but why I received the correct answer (the computer name which got the server's IP) is a mystery to me.


DHCP and DNS are two entirely different things.

In a network environment the concept of DHCP is effectively to dish out internal IP addresses to devices that request them and prevent conflicts of IP addresses because if two devices have the same IP, neither will be accessible. However if your DHCP server falls over, the machines may not automatically renew their addresses until they time out, and this is a common cause of IP conflicts.

The act you change your DNS servers only means that your internal network one isn't working and that's probably because your DHCP server has fallen over. If your network is set up in such a fashion that the server handles all the network and internet traffic, and that falls over on the DHCP side of things so it's all wrong, all that means is you changing your settings mean the system will use whatever you've set. Caching has nothing to do with it.
  • 0






Similar Topics

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users

As Featured On:

Microsoft Yahoo BBC MSN PC Magazine Washington Post HP