[dns-operations] Limit on Name Servers & their IPs for a sub-domain

James Stevens James.Stevens at jrcs.co.uk
Thu Jan 11 15:11:00 UTC 2018

I am aware of the "traditional" limit of 13 NS records for a sub-domain, 
is it considered that this still applies?

A live test I ran indicated that multiple IPv4/IPv6 records for the name 
name server get (roughly) the name number of queries.

But, I only tested a small number of address - is there some reason 
(e.g. packet size, code restrictions, etc) that might mean more 
addresses would not scale?

This suggests a theoretical unlimited servers for a sub-domain, so long 
as they are represented as additional IP Addresses against the same name.

Is there any practical / theoretical / recommend limit ?

I have seen a lab test that used two Class-A addresses and showed that 
all IPs received queries, but it was using a very limited range of 
vendor equipment.

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