Yes that's true. But its pretty tough to convince to management team that as a business strategy you can not create multiple identical domain or add same service section to multiple website. They always see as a business point of view & reducing resources on it. On the other side as we are getting million of traffic from all domains even from search engine. So they think that is there any strategy for duplicate content.
No! They need to change their business strategy to NOT expect, need or want traffic from search engine results.
It is NOT a sensible strategy to rely on getting business and earnings from a source that is not within your control, may or may not send converting traffic, or may simply stop sending traffic one day with no warning, no right of appeal and no indication of why it has dried up.
You could put a robots meta tag with content of "noindex, follow" instead of "noindex, nofollow." That way, search engines will crawl those pages and discover links on them, but won't add them to the index.
The rel-canonical method would involve putting a tag on the duplicate pages indicating that the one page you want indexed is the canonical version of that content. The tag would also go on the page you want index, so it would be declaring itself to be canonical as well. The advantage to doing it that way is that Google may view the duplicates as a group, so that if anyone links to one of those page it will count, at least in part, as a link to the canonical page. I can't guarantee it will accomplish that, but people whose knowledge of these things I trust have told me it works. I've just never seen clear evidence of it working, since you can't really demonstrate that a link to a non-canonical page actually provides a boost to the canonical one.
I can pretty much guarantee you'll avoid duplicate content issues with either of those methods.
Yes, even I am also following strictly search engine algo as a part of duplicate content but I need some strong statement to convince management team about duplicate content issue across all domains. That's why I came to this forum & want some strong words from any expert like you At last one quick question: I am little confused that can we apply canonical tag to cross domain ? Suppose we have three different identical domain & can we add canonical tag to one potential domain? like 1. site.com 2. abc.com, 3. domain.com