Quote:
Originally posted by greyhammer
I mean, how does, dns1.isp.com maintain an SOA for mydomain.com?
More than midly curious,
Thanks!
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Your question is confusing, but I think I understand what you are asking
A DNS server can only be authoritative for the zones it loads, but it can answer queries for other domains (like yahoo.com), but it is NOT authoritaive for yahoo.com. It simply caches the results for future queries.
Example:
Code:
C:\>nslookup
Default Server: ns1.mydomain.com
Address: 192.168.9.4
> www.mydomain.com
Server: ns1.mydomain.com
Address: 192.168.9.4
Name: www.mydomain.com
Address: 192.168.9.2
> www.yahoo.com
Server: ns1.mydomain.com
Address: 192.168.9.4
Non-authoritative answer:
Name: www.yahoo.akadns.net
Addresses: 68.142.226.34, 68.142.226.48, 68.142.226.53, 68.142.226.46
68.142.226.33, 68.142.226.39, 68.142.226.36, 68.142.226.45
Aliases: www.yahoo.com
A couple of things to notice about the above:
1) The query for
www.mydomain.com was authoritative - meaning that the zone for mydomain.com is loaded on my DNS server.
2) The query for
www.yahoo.com was answered by my DNS server, but the reply was non-authoritative. Meaning that my DNS server does not load the yahoo.com zone file. It had to first goto the root name servers to find the SOA for yahoo.com and then query yahoo's name server (which is authoritative) to finally return the answer. In DNS terminology, this is called recursion.
A good example of recursion can be demonstrated by using dig's trace option. Example:
# dig +trace
www.yahoo.com a
BTW: Your ISP's name server works in the same way. Although they probably have separate DNS servers. One's that are authoritative for their domains and others that are configured as caching-only. The caching only servers do not load any authoritative zones and are typically queried by their customer base. i.e. resolv.conf points to these caching only servers.