Question 1

Does this work with Comcast?

Accepted Answer

I would assume it would, our area has ATT, Windstream, and Time Warner.  Also assuming since Comcast, but not in my area,  is a cable provider like Time Warner (Time Warner works with this) it should.  Cable comes in through a modem and distributed to your phone service and ethernet to your pc or router.  TW works greats.  I also, made a porabula to amplify the signal in a specific direction that increased my wireless speed to other devices, made of foil glued to paper and place behind the router to direct it toward those devices.

Question 2

Does this support Chromecast?

Accepted Answer

Yes.  At least it should work.  Ideally you want a plugged connection for streaming since 'wireless' is not as reliable nor 'fast enough' quite yet for streaming as a whole.  You will likely see some screen quality issues and things like that.
We stream wirelessly to our iPhone and Kindle Fire and our router is not even this Dlink (we have a Netgear).  We don't specifically use Chromecast but it is the same concept :)  we bought this Dlink for my wife's parents as their old router kept dropping connection - no complaints yet!

Question 3

operating frequency?

Accepted Answer

2.4GHz

Source:
All Wireless N Routers are not Created Equally
By Randall Sutherland

Question 4

Does this installation CD come with mac instructions?

Accepted Answer

I actually don't recall if it does come with any specific Mac instructions, but I don't use the install CDs anyway.  You can simply aim a browser at the default address for the router and configure it from there

Question 5

Can you use a USB splitter to put more then one USB item in the router?

Accepted Answer

No but you can use a USB hub. And maybe that's what your calling a USB splitter.  If its a mouse or something like that any USB hub should work.  If its a printer or larger device you might need a Powered USB hub.

Question 6

Does the router have a log that the user can export to an external file? In particular, security events.

Accepted Answer

Under "tools" setup it has a log and it can email it to you, or it supports a "syslog" server if you have one on your network, but I don't know what type of security events it logs.

Questions & Answers