[TriLUG] [Possibly OT] Changing ISPs

[Matt Nash]

Christopher J. Knowles wrote:
> Once again, I appear, hat in hand, prostrate at the altar of the amassed 
> knowledge of TriLUG...
>
> My company is being forced to move ISP's.  (Level3 is dropping anything so 
> rinky dink as our 300 people...)  It's already been decided by the muckety 
> mucks who we're going with... 
>
> My problem is this... 
>
> The change over will happen sometime in the next few months... and I would 
> like to make sure that inbound e-mail and web traffic doesn't get lost.  (or 
> at least that the loss is a minimum...)
>
> Now, we run our own DNS servers, and I'm perfectly capable of maintaining 
> normal events, but this is a little bit beyond me.  
>
> So my question is this... what's the right sequence of events to make 
> everything go smoothly?
>
> CJK
>   
Having shepherded this process for several different companies, I would 
suggest that the most important thing is to develop a relationship with 
a good technical person at the new ISP.  Talk to them several times 
during the week leading up to the switch to make sure everything is in 
place.  If you can get a visit from a real live engineer to verify that 
everything is physically connected and ready to go, well in advance of 
your switch, everything is more likely to go smoothly.  Even so, you 
should plan for something to go wrong, because it usually does.

If they can plan to have the circuit turned up more than 1 week in 
advance, you can test the switchover yourself -- try to bring the new 
circuit online one evening or weekend, with enough time to spare before 
your real switchover occurs.  If you have spare equipment or are getting 
new equipment (CSU/DSUs, routers, etc) this is a little less hairy.  
ISPs have to work with whoever owns your building's demarc to get 
everything right, and telecom companies do not play well with each 
other.  Verifying in advance that the circuit and the routers are 
properly configured will save you from a stressful late night.

For minimum email disruption, you should find someone who will queue 
your email for free -- most likely your new ISP.  If free isn't 
available, I have had good results with magma -- www.magma.ca.  All that 
is required, once they have agreed to queue your email, is to add their 
server as a lower-priority MX record.  This is good to have in place 
even when you aren't switching ISPs.

For minimum DNS disruption, lower your zone's TTLs to about 15 minutes, 
several days in advance of the switch.  This will force all downstream 
clients and DNS servers to look up your DNS records nearly every time, 
rather than using cached lookups.  Hosting your own DNS puts you in a 
good position, not having to rely on your domain's registrar to switch 
DNS servers.

Good luck!

Matt