I have an ecommerce website with 4 departments, that share the same categories,
For example a bicycle shop would have different products for mountain biking and road cycling, but they would both share the same 'tyres' category.
I get around this by having the department as a filter, that changes the products on show, and adds a URL parameter of ?department=1.
When this filter is applied, i have a canonical link setup to the non-filtered category. Any filter links are nofollowed.
My top menu has 4 different sections, one for each department, and links to these URLs with the department parameter already on, these links are set to allow robots to follow.
As i am actively pointing Google at these pages, and it is my main navigation, should the page they go to be noindexed? As its the canonical i want to rank.
Hopefully this makes sense.
Cheers