I recently installed phpbb3 (first time) and everything seems fine except that when making the site map, the same topic is crawled 5 times. After modifying the robots.txt using
User-agent: *


Disallow: /forum/phpBB3/viewtopic.php?p=
Disallow: /forum/phpBB3/viewtopic.php?=&p=
Disallow: /forum/phpBB3/viewtopic.php?t=
Disallow: /forum/phpBB3/viewtopic.php?start=
Disallow: /forum/phpBB3/*&view=previous
Disallow: /forum/phpBB3/*&view=next
Disallow: /forum/phpBB3/*&sid=
Disallow: /forum/phpBB3/*&p=
Disallow: /forum/phpBB3/*&sd=a

It has reduce to 4 times per topic. (only "viewtopic.php?p=" is disallowed) I notice that files having /*&sid=, /*&sd=a, and start=, are not blocked. Puzzling though, is that if I substitute the p for f as in "viewtopic.php?f", everything is disallowed. Can you help please?

Are you using a vanilla phpbb3 or the phpbb3 Premod or?

Is your forum indeed installed in /forum/phpBB3/ as well ?

If you do not use any url rewriting, then you will still have duplicates.
If you where previously using phpBB2 and converted, then you should drop the viewtopic.php?t= line, because the old topic urls where of that form.

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I am using Phpbb3 prosilver as downloaded and it is installed in
-www.domain.com\forum\phpBB3.
I will drop the viewtopic.php?t= line and see what happens.
Thanks much for your help.