sorry but i don't understand why it's a problem for you how zenoss work,

actually in zenoss you can give device dependency (at l3 via cli)

This is a complex and interesting item already discussed in lot of posts. If you search in the forum for "layer3 dependencies" will find lot of informations. In my opinion one of the best post (in which I have discussed) is thread/12061?start=0&tstart=0

Basically zenoss manage layer3 dependencies automatically if it is able to read and learn routing tables of all of the devices involved in the communications. When not possible, you can write python code (as suggested by Consadori) although I think that this is not always good in fact I opened a "future request" (I'm enterprise customer) about the ability to manually create dependencies in "nagios style" that, in this case, is absolutely better than zenoss.

Unfortunately if you speak about the "port of the switch", you speak about "layer2 topology" and, in this case, zenoss doesn't handle layer2. Anyway I think that using layer3 with manual dependencies you should be able to reach your goal (at least partially). You won't say: if port3 of the switch is down then...but you should be able to say(at least) : if swith goes down...then suppress events for those servers attached to this switch.

I hope to have clarified your doubt.

bye

Marco