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Old 03-28-2006, 10:28 AM   #1
redsfan
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Registered: Mar 2006
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Comcast changing to dynamic DNS


Hi,
I have received several notes from Comcast (my ISP) that they are changing their DNS system, and that my PC “must be configured for dynamic DNS communication”. This needs to be done by 3/31/06.

I have a Linux server running Fedora Core 4. I use this server to share this Comcast internet connection for a number of Linux & Windows clients (NAT in iptables). I also use this server as a DHCP server and push DNS settings to the Windows & Linux clients vis DHCP. I currently have the DNS server ip addresses configured to Comcast's current (old?) DNS servers. Specifically, in resolv.conf on the server I have Comcast's old ip addresses and in dhcpd.conf I also have Comcast's old ip addresses which push out to the clients. With the change that Comcast is making, I assume the DNS addresses I currently am using will no longer work.

Seems like I have 2 choices. Change my DNS settings to one of the many public DNS servers or change my setup to use dynamic DNS. I have googled and found public dns servers that are available for use, but the response is slow. Does anyone know what changes I need to make to my server in order to use dynamic dns?

TIA,
Steve
 
Old 03-28-2006, 11:51 AM   #2
mrclisdue
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Register an account with no-ip.com or dyndns.org; download and configure their update client, and you're set for life.

cheers,
 
Old 03-28-2006, 12:47 PM   #3
redsfan
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Hi,
Thanks for the info. I will look into those 2 sites that you mentioned.

Do you know if these dynamic dns clients will update the dhcp configuration on my server so that the clients on my network get updated dns info? Or do all of the clients on the network have to run the dynamic dns client also?

Anyone know if there is a howto or step-by-step setup guide on dynamic dns?

Also, I have not ruled out the idea of using a "public" dns server. Anyone know how I can determine if a dns server is physically near my location so I get quick response?

Thanks,
Steve
 
Old 03-28-2006, 02:18 PM   #4
mrclisdue
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Regarding your dns issues, unless Comcast has indicated otherwise, there's no reason for them to change their dns servers.

As far as notifying your clients of the 'new' dns address, I would use your server's ip, since your server is the gateway anyway.

So, only your server should run the update client.

cheers,
 
Old 03-28-2006, 03:20 PM   #5
Darin
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Seems to be some confusion in this thread. no-ip.com and dyndns.org provide dynamic DNS resolution for their customer domains on changing IP addresses. Comcast, as an ISP, provides DNS servers for their customers to use to look up all names on The Internet. Comcast (aside from not knowing half of richard about being an ISP) from what it sounds like is just changing their DHCP server.

Unless I missed something, what they are calling "dynamic DNS" is simply that they will add the DNS servers to the information that is given out when your [PC/Router] gets assigned an address from Comcast. Barring that they actually change the public IP addresses of their DNS servers (changing the public IP of your nameservers is considered A bad thing and is rarely done) everything you have set now will work fine after they change whatever it is they are changing.

I don't think you will find a FAQ on how to set up clients to automatically get a DNS server from DHCP, this is what is known as "default" setting.

Also if you "use your server's ip [for DNS], since your server is the gateway anyway" your server has to have DNS service running on it as well. It sounds like it wouldn't be a bad idea to set up a DNS server on that box anyway, in order to avoid confusion with the cable company turned ISP. You can search here or on The Internet in general to find info on setting up a DNS server.
 
Old 03-31-2006, 04:41 AM   #6
win32sux
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yeah, just setup dnsmasq on the gateway box and configure your dhcp server to give the clients on the LAN the internal address of the gateway as the DNS server... this way the clients don't need to know which DNS server address comcast is using, only the gateway box will need to know... since it sounds like the gateway's configuration will change to dhcp you'll also want to change any SNAT iptables rules to MASQUERADE, so that they'll work no matter what IP your external interface gets... so basically if you set everything right you won't have to worry about any configuration changes anymore...

AFAICT the no-ip.com (etc...) stuff has nothing to do with any of this...

Last edited by win32sux; 03-31-2006 at 04:43 AM.
 
  


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