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nslookup - tld - inconsistent results

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  • nslookup - tld - inconsistent results

    OK, so this problem has been bugging me for ages. I find it no matter where I use nslookup, different servers / sites.

    I find that sometimes I cannot get the same result returned when I
    query TLD servers for NS records. I'm sure there is something I am misunderstanding.

    Take the domain name bbc.co.uk

    I want to find out what servers look after uk. and then from the servers responsible for the uk. domain I want to query where the NS records are for bbc.co.uk.

    So using nslookup:

    nslookup
    set q=ns
    .

    Returns the root servers. I pick one and run a query:

    lserver b.root-servers.net
    co.uk.

    I get a list of servers responsible for uk. domain, I pick one and run a query:

    lserver nsa.nic.uk
    bbc.co.uk.

    And I get this:

    Server: nsa.nic.uk
    Addresses: 2001:502:ad09::3
    156.154.100.3
    *** nsa.nic.uk can't find bbc.co.uk.: No response from server

    So, I go through the list of servers ns1-7.nic.uk, nsa-d.nic.uk and find that some work and some don't. Then after a while, they all start returning the results properly.

    I think it is either I am not using the tool properly, or there is some form of security / intermittent refusal when trying to query the same record multiple times from same IP? Anyone able to shed any light?

    Thanks guys
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