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Are there any problems with having multiple wildcard dns entries for a domain?

Eg:

CNAME  *.a.example.com  1.1.1.1
CNAME  *.b.example.com  2.2.2.2
CNAME  *.example.com    3.3.3.3

I have this set up currently with DNSimple and it all seems to work ok, I'm just wondering if there are any potential issues.

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I generally avoid wildcard entries as they cause a lot of unexpected problems. –  mdpc Jan 4 '13 at 0:28

2 Answers 2

up vote 1 down vote accepted

With wildcard cname or a record, people can reach your site using

Any_Combination_Of_Inappropriate_Or_Embarrassing_Word.yourdomain.com

If some page in the wild link to your site with the above, when they indexed by search engine, your site may be associate with search item/terms/words you don't want. And you really have no control.

The above is the main reason I stay away from wildcard dns record.

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I think this is only partially true: nothing prevents you from using robots.txt et al to prevent indexing such unknown domains of yours, plus nothing prevents the attacker from linking to your site with various inappropriate words, either. But, in general, I, too, agree with the idea that wildcard DNS is kinda evil. Unless there is some good reason why they have to be used, they shouldn't just be used for the sake of wildcardness. –  cnst Jan 4 '13 at 4:08
    
@cnst Being index in such way maybe the worst case scenario. Allowing the site/machine to be accessed in such away is an embarrassment. Sometimes in-house / inside jokes may lead to consequences. –  John Siu Jan 4 '13 at 4:16

No, there's no problem with doing that.

It may help to think of those as different domains.

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