Multiply domains and duplicate content confusion

[bisibee1]

I've just found out that a client has multiple domains which are being indexed by google and so leading me to worry that they will be penalised for duplicate content.  Wondered if anyone could confirm a) are we likely to be penalised? and b) what should we do about it?  (i'm thinking just 301 redirect each domain to the main www.clientdomain.com...?).

Actual domain = www.clientdomain.com

But these also exist:

www.hostmastr.clientdomain.com

www.pop.clientdomain.com

www.subscribers.clientdomain.com

www.www2.clientdomain.com

www.wwwww.clientdomain.com

ps I have NO idea how/why all these domains exist

I really appreciate any expertise on this issue, many thanks!

[Highland]

Depends on why the subdomains exist. If they're all carbon copies you might have an issue on your hands. If they're just various content, I wouldn't worry about it. Incidentally, some hosting programs (like Plesk, cPanel, etc.) will create a specific set of DNS entries for you automatically if you're not careful so that could be the source of some of this mess.

Should you consolidate domains? That depends. Are any of these subdomains penalized? Are they ranking better than your root site? Are they getting traffic? I would do your homework before consolidating. In some cases it might be better to just turn them off.

[billhartzer]

Fiona,

Just to be clear, what you're referring to are subdomains, and not domains. You're right, though, there are definitely issues related to duplicate content that is going to cause ranking problems. Typically, Google will rank the content that they crawled first: the others will be the duplicates.

The best way to deal with this is to decide which subdomain you really want: which will typically be www.clientdomain.com and then 301 redirect all of the others to www.clientdomain.com.

If, however, there is unique content on the other subdomains, then you wouldn't want to redirect those.