Re: Network connection diagnostics

Moe Trin a écrit :

Contrary to the mystique, most ISPs do
not move their name servers around that much, because of the hassle of
getting the word of the new address out to the world.

Such hassle exists only when the ISP uses the same servers as cache NS for their customers and as authoritative NS for their domains. The world doesn't care a damn about which cache servers the customers use.

I've got four ISPs, two of which I've had for more than five years. NONE
of them have swapped DNS IPs.

I have one ISP, and they changed one of their cache DNS at least once. Actually, one server used to be a cache+authoritative DNS and became authoritative only, and another server took over the cache function.

Honest and true, most people have better things to do than to move the
name servers (and routers, and well known servers) around for no good
reason.

Sure. When they do so, they have a good reason.
Reasons that come to my mind are related to network evolution.

1) Network growth. A small ISP begins its business. They use the same servers to host multiple services such as authoritative and cache DNS, FTP, MX... Then the customer count increases and so does the servers' load, so the services are divided on separate servers. The IP address of some service will have to change. Or the ISP sets up additional cache DNS to share the load and "tells" some customers to use the new DNS depending on their location.

2) Network agregation. Two or more formerly independent network, each using their own set of cache DNS, are merged for whatever reason. It is decided that eventually only one set of DNS will be kept. So the hosts which used the other set of DNS will have to swap.
.

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