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On Windows, I do ipconfig /displaydns

One record is:

 na4.salesforce.com
 ----------------------------------------
 Record Name . . . . . : na4.salesforce.com
 Record Type . . . . . : 5
 Time To Live  . . . . : 8
 Data Length . . . . . : 8
 Section . . . . . . . : Answer
 CNAME Record  . . . . : na4-was.salesforce.com

I see no IP for it.

How does Windows resolve the IP for this then?

Note: there is no other entry for na-4-was.salesforce.com.

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1 Answer

up vote 1 down vote accepted

CNames or canonical names basically let you alias one domain name to another - this makes it simpler if you have lots of domain names pointing at the same server - for example, you had seperate domain names for FTP, different domain names for vhosts and so on.In this case na4.salesforce.com points at na4-was.salesforce.com, which then points at somewhere else.

If you run tracert on na4.salesforce.com, it'll look up na4-was.salesforce.com

and you get

C:\Users\geek>tracert na4.salesforce.com

Tracing route to na4-was.g.salesforce.com [96.43.150.52]
over a maximum of 30 hops:

Which means it simply resolves the ip address for the domain na4-was.g.salesforce.com when you ask for na4-was.g.salesforce.com.

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1  
So it never caches it? And has to resolve it each time? –  dublintech Jun 17 '12 at 10:13
    
Apparently not. Bizarrely tracert-ing na4-was results in it showing up as a cname for itself... which makes no sense at all. –  Journeyman Geek Jun 17 '12 at 10:17
    
@dublintech, sorry, why do you think cname records aren't cached? They are cached like anything else. –  Zoredache Jun 17 '12 at 10:28
    
@Zoredache there was no corrresponding entry for the cname record in the cache, in this case. –  dublintech Jun 17 '12 at 20:16
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