add note on delegation
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AJ ONeal
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168
HOW_DELEGATION_WORKS.md
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168
HOW_DELEGATION_WORKS.md
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DNS Delegation
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==============
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Tracing NS records trying to understand DNS delegation better.
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Root Servers
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------------
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The root servers will return the TLD records for any domain
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```bash
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dig A @m.root-servers.net www.example.daplie.me
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```
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```
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; <<>> DiG 9.8.3-P1 <<>> A @m.root-servers.net www.aj.daplie.me
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; (1 server found)
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;; global options: +cmd
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;; Got answer:
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;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34843
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;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 5, ADDITIONAL: 10
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;; WARNING: recursion requested but not available
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;; QUESTION SECTION:
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;www.aj.daplie.me. IN A
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;; AUTHORITY SECTION:
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me. 172800 IN NS c0.nic.me.
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me. 172800 IN NS b0.nic.me.
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me. 172800 IN NS a0.nic.me.
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me. 172800 IN NS b2.nic.me.
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me. 172800 IN NS a2.nic.me.
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;; ADDITIONAL SECTION:
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a0.nic.me. 172800 IN A 199.253.59.1
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a2.nic.me. 172800 IN A 199.249.119.1
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b0.nic.me. 172800 IN A 199.253.60.1
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b2.nic.me. 172800 IN A 199.249.127.1
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c0.nic.me. 172800 IN A 199.253.61.1
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a0.nic.me. 172800 IN AAAA 2001:500:53::1
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a2.nic.me. 172800 IN AAAA 2001:500:47::1
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b0.nic.me. 172800 IN AAAA 2001:500:54::1
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b2.nic.me. 172800 IN AAAA 2001:500:4f::1
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c0.nic.me. 172800 IN AAAA 2001:500:55::1
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;; Query time: 141 msec
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;; SERVER: 202.12.27.33#53(202.12.27.33)
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;; WHEN: Tue Oct 3 15:47:25 2017
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;; MSG SIZE rcvd: 343
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```
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GTLD Servers
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------------
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The GTLD Servers will return the glue records for the nameserver which hosts the SLD in question
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```bash
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dig A @b0.nic.me www.aj.daplie.me
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```
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```
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; <<>> DiG 9.8.3-P1 <<>> A @b0.nic.me www.aj.daplie.me
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; (1 server found)
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;; global options: +cmd
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;; Got answer:
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;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52062
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;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 0
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;; WARNING: recursion requested but not available
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;; QUESTION SECTION:
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;www.aj.daplie.me. IN A
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;; AUTHORITY SECTION:
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daplie.me. 86400 IN NS ns2.redirect-www.org.
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daplie.me. 86400 IN NS ns1.redirect-www.org.
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;; Query time: 29 msec
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;; SERVER: 199.253.60.1#53(199.253.60.1)
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;; WHEN: Tue Oct 3 15:48:41 2017
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;; MSG SIZE rcvd: 86
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```
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If the nameserver were "in bailiwick" then it's A/AAAA records would be returned in an additional section.
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SLD Nameservers
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---------------
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There are three main conditions:
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* Exists
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* Doesn't exist (but lives here)
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* Delegated
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There's also the condition of *"doesn't exist (and doesn't live here)"*, but we'll save that for another day
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(or try `dig @ns1.google.com A yahoo.com`).
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### Exists
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```bash
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dig A @ns2.redirect-www.org www.aj.daplie.me
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```
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```
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; <<>> DiG 9.8.3-P1 <<>> A @ns2.redirect-www.org www.aj.daplie.me
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; (1 server found)
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;; global options: +cmd
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;; Got answer:
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;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52373
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;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
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;; WARNING: recursion requested but not available
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;; QUESTION SECTION:
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;www.aj.daplie.me. IN A
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;; ANSWER SECTION:
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www.aj.daplie.me. 300 IN A 45.56.59.142
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;; Query time: 83 msec
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;; SERVER: 66.172.33.29#53(66.172.33.29)
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;; WHEN: Tue Oct 3 15:57:14 2017
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;; MSG SIZE rcvd: 50
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```
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### Doesn't Exist (but would)
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```bash
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dig A @ns2.redirect-www.org doesntexist.aj.daplie.me
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```
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```
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; <<>> DiG 9.8.3-P1 <<>> A @ns2.redirect-www.org doesntexist.aj.daplie.me
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; (1 server found)
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;; global options: +cmd
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;; Got answer:
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;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19993
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;; flags: qr aa rd; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
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;; WARNING: recursion requested but not available
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;; QUESTION SECTION:
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;doesntexist.aj.daplie.me. IN A
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;; AUTHORITY SECTION:
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daplie.me. 1 IN SOA ns1.redirect-www.org. hostmaster.daplie.me. 2017020100 10800 3600 1209600 1800
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;; Query time: 68 msec
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;; SERVER: 66.172.33.29#53(66.172.33.29)
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;; WHEN: Tue Oct 3 15:59:25 2017
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;; MSG SIZE rcvd: 109
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```
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### Delegated Subdomain
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Should look something like this, I'm pretty sure:
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```
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;; QUESTION SECTION:
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;john.daplie.me. IN A
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;; AUTHORITY SECTION:
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john.daplie.me. 86400 IN NS ns2.dns-host.org.
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john.daplie.me. 86400 IN NS ns1.dns-host.org.
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```
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I think that in practice anything matching `*.john.daplie.me` would be delegated,
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but I but you could do something weird like host `whatever.john.daplie.me` on the original
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nameserver by A) answering to it directly on the main nameserver and B) delegating
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from `whatever.john.daplie.me` back to the original nameserver in case the resolving
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client makes intelligent assumptions and caching.
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