DNS: Difference between revisions
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| 8.8.4.4 || [https://developers.google.com/speed/public-dns/ Google] || Global (routed via [http://en.wikipedia.org/wiki/Anycast Anycast]) | | 8.8.4.4 || [https://developers.google.com/speed/public-dns/ Google] || Global (routed via [http://en.wikipedia.org/wiki/Anycast Anycast]) | ||
|- | |||
| 156.154.70.1 || [http://www.dnsadvantage.com/index.html DNSadvantage] || [http://www.dnsadvantage.com/dnsadv/node_locations.html Global] | |||
|- | |- | ||
| 156.154. | | 156.154.71.1 || [http://www.dnsadvantage.com/index.html DNSadvantage] || [http://www.dnsadvantage.com/dnsadv/node_locations.html Global] | ||
|- | |- | ||
| | | 208.67.220.220 || [http://www.opendns.com/ OpenDNS] || [http://www.opendns.com/technology/network-map Global, mainly US] (routed via [http://en.wikipedia.org/wiki/Anycast Anycast]) | ||
|- | |- | ||
| 208.67.220. | | 208.67.220.222 || [http://www.opendns.com/ OpenDNS] || [http://www.opendns.com/technology/network-map Global, mainly US] (routed via [http://en.wikipedia.org/wiki/Anycast Anycast]) | ||
|- | |- | ||
| 4.2.2.1 || Level 3 || Probably global (routed via [http://en.wikipedia.org/wiki/Anycast Anycast]) | | 4.2.2.1 || Level 3 || Probably global (routed via [http://en.wikipedia.org/wiki/Anycast Anycast]) | ||
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http://theos.in/windows-xp/free-fast-public-dns-server-list/ | http://theos.in/windows-xp/free-fast-public-dns-server-list/ | ||
== NSLookup == | == Troubleshooting == | ||
=== NSLookup === | |||
NSLookup is a Name Server Lookup/Query tool which exists in both Unix and Windows distributions, and generally speaking, functionaly the same regardless of which version you're using. To start, run <code>nslookup</code> from the command line. | NSLookup is a Name Server Lookup/Query tool which exists in both Unix and Windows distributions, and generally speaking, functionaly the same regardless of which version you're using. To start, run <code>nslookup</code> from the command line. | ||
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> | > | ||
=== Propagation === | |||
One of the features of DNS is the way that records get cached around the globe. Meaning that any changes to existing records have to ripple around. Generally changes take up to 72 hrs (3 days) to take effect. | |||
However, you can change the [[Acronyms#T|TTL]] of record to ensure that it needs to be refreshed from its authoritative name-server more frequently than normal, ensuring that any changes apply more quickly. | |||
'''To view the propagation of a record around the world see http://www.whatsmydns.net''' | |||
=== General === | |||
The following site has a number of tools that allow you to investigate how a domain is viewed externally/publicly... | |||
http://enc.com.au/itools/ | |||
== Notes == | == Notes == | ||
Latest revision as of 22:34, 20 February 2013
DNS Servers Open to Public Query
This is not an exhaustive list of publicly accessible DNS servers. There are more, those listed below are a subset, and may be better or worse than others.
| IP Address | Provider | Location |
|---|---|---|
| 8.8.8.8 | Global (routed via Anycast) | |
| 8.8.4.4 | Global (routed via Anycast) | |
| 156.154.70.1 | DNSadvantage | Global |
| 156.154.71.1 | DNSadvantage | Global |
| 208.67.220.220 | OpenDNS | Global, mainly US (routed via Anycast) |
| 208.67.220.222 | OpenDNS | Global, mainly US (routed via Anycast) |
| 4.2.2.1 | Level 3 | Probably global (routed via Anycast) |
| 4.2.2.2 [1] | Level 3 | Probably global (routed via Anycast) |
| 194.72.9.34 | BT | UK |
| 194.72.9.34 | BT | UK |
Sources: http://theos.in/windows-xp/free-fast-public-dns-server-list/
Troubleshooting
NSLookup
NSLookup is a Name Server Lookup/Query tool which exists in both Unix and Windows distributions, and generally speaking, functionaly the same regardless of which version you're using. To start, run nslookup from the command line.
| Command | Description |
|---|---|
server |
Displays the DNS server(s) currently being used by nslookup |
server 8.8.4.4 |
Changes the DNS server being used/queried to 8.8.4.4 |
host.domain.com |
Attempts to resolve host.domain.com against current DNS server
|
109.123.76.85 |
Attempts a reverse lookup for IP 109.123.76.85 against current DNS server
|
set q=mx |
Set query type to MX (subsequent queries will look for Message Exchange (email) records)
|
set q=all |
Set query type back to all records |
exit |
Quit nslookup |
For example, to find the email exchange servers for a particular domain...
> set q=mx > microsoft.com Server: [8.8.4.4] Address: 8.8.4.4 Non-authoritative answer: microsoft.com MX preference = 10, mail exchanger = mail.messaging.microsoft.com >
Propagation
One of the features of DNS is the way that records get cached around the globe. Meaning that any changes to existing records have to ripple around. Generally changes take up to 72 hrs (3 days) to take effect.
However, you can change the TTL of record to ensure that it needs to be refreshed from its authoritative name-server more frequently than normal, ensuring that any changes apply more quickly.
To view the propagation of a record around the world see http://www.whatsmydns.net
General
The following site has a number of tools that allow you to investigate how a domain is viewed externally/publicly...
Notes
- ↑ For further info on 4.2.2.2 see http://www.tummy.com/Community/Articles/famous-dns-server/