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Changing ISP, updating DNS

Re: Changing ISP, updating DNS

Date: Friday, March 10, 2000
Time: 4:01:00 am

hi all,

I'm about to switch ISPs. The old isp's line is up and the new isp's line is also up. I search site for a howto on changing but didn't find one...

From reading this thread of messages I've come up with this perliminary plan to switch services from the old addresses to to the new addresses.

1. Change the ttl's for each domain down to 1 hour (3600) on the primary name server. (which I did about an 6:30pm pst...)

2. I'll move the secondary dns server to the new network sometime in the next day or too...

3. Update all the primary records to reflect the new secondary server...

4. Move the least used server (or service) to the new network connection and update the primary dns pointing to it's new home.

5. Repeat 4 for each server.

6. When the last server on the old network is the primary DNS then I'll setup a temporary dns server to act as a primary on the new network. Update Internic records. And wait...

7. Once primary dns changes are reflected by Interic. Then shut down the old network. move the old primary dns to the new network to replace the temporary...

So. is this a reasonable course of action to pursue? Any pitfalls or
variations that make the switch over easier/better...

Thanks for any advice.

Re: Changing ISP, updating DNS

From: Men & Mice Support
Date: Saturday, January 15, 2000
Time: 12:53:00 am

At 10:55 AM +0000 1/14/2000, Mark Palmer, Pageworks wrote: I think I got it backwards in my original post. Tell me if this thinking is correct.
>1. I change the TCP/IP control panels on each of web, mail and DNS
>to the new IP numbers
>2. I make an additional Mac IP Multi-homing entry using the OLD IP
>number for that machine.
>3. I amend all my domains in QDNS to the new IP range.
>4. I update my records at Nominet (the UK naming authority), I think
>this only really effects which host name they look for for
>secondary. Please tell me if I'm wrong!
>Then presumably what is now stale data within the DNS as a whole
>will find a host on the old number, and as the DNS updates itself,
>QDNS will respond with the new data as time clicks on. Am I correct
>in thinking there is no need for me to run a second copy of QDNS
>using the OLD IP number, becuase some other DNS server is going to
>resolve those numbers temporarily.

Bad order of operation. What you've outlined would take down at least your DNS services, and possibly others, until everything is updated.

I've taken a look at your DNS, and I see a better way to do this, based on the fact that you already have two DNS server of your own (plus one at your old [?] provider) and the fact that none of your services appear to be on the same machine. In other words, ns1, ns2, mail, and www (in the domain) are all different machines.

1) Move to its new address - change the address in TCP/IP.

2) Ask Nominet (who I take it is the domain registrar of commercial domains in the UK) to change your registration records for, which should have the effect of updating the rest of your domains as well. Your new records should point to both ns1 and ns2 (and, if you're going to continue using this server), but use only the new addresses. Don't worry about the fact that the addresses aren't all yet in use; ns2 will take the load by itself.

3) Add secondary addresses to all your other servers. Don't bother with your QuickDNS Pro servers, since they won't see the extra addresses anyway. (Make sure all your other services support multiple addresses - I'm not sure about CommuniGate.) Configure all these services to use their new extra addresses. (You can either put the new addresses in Secondary Addresses, or switch them; it doesn't matter.)

4) Now start changing your DNS records for all your domains to point to the new addresses. Since all services are in place on both subnets, there will be no disruption of services. When all is changed, reboot your secondary server. Ask your provider to reboot, too.

5) Wait. You'll need to wait at least (TTL + TTL of delegation records) seconds from the time the delegation records are changed, or (TTL) seconds from the time the DNS records are changed, whichever is longer. Currently, your delegation records have a 4 hour TTL, and your own records have a 24 hour TTL; you can turn down your TTL beforehand to minimize this, but then remember to wait for the new TTL to be noticed - a wait of at least (old TTL) seconds.

6) Take down all your old addresses. Move ns1 to its new address. If you're not going to be using's servers anymore, ask them to remove their settings for your domains (both DNS and mail).

>If I happily start editing each domains details in QDNS what can I
>expect to happen and when? How long before the rest of the world is
>up to date? I'm using whatever default value of TTL QDNS shipped
>with. Can I drop this value now to a couple of minutes, without
>changing the IP numbers, allow this to propogate around the world
>and then change the IP numbers and bump the TTL back, hoping things
>will update faster.

Dropping it to a couple of minutes is extreme, as this will cause extra DNS traffic on your lan. 1 hour (3600) isn't out of line, though.

>Are there certain times of the day when root servers update
>themselves, if so can I take advantage of this?

None of your information on the root servers needs to be changed, except possibly to remove your old ISP's DNS server. They refer to your DNS servers by name only, since you're in the UK domain.

Unfortunately, you can't time the root servers anyway, since they have to be modified by the domain registrar (probably Network Solutions), and the first person who can accurately predict when NetSol will do anything could probably make a fortune.

The root servers are updated once every 48 hours. I don't recall when, exactly, though.
Chris Buxton [email protected]
Men & Mice
Makers of: QuickDNS Pro



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