N600 access

> I currently have a R6300v2 router running my network. [...]

   Firmware version?

> [...] I have a N600 WNDR3400 that I'm trying to configure. [...]

   WNDR3400[v1], WNDR3400v2, or WNDR3400v3?  Look at the product label.
Firmware version?

   Why?  Are you trying to replace the R6300v2, or add the WNDR3400 to
your existing network for some reason or other, or what?

> [...] I have the R3400 hooked to my laptop with a CAT5 cable however
> when I got to http://www.routerlogin.net it shows the R6300 access page.

   "R3400"?  "WNDR3400[vX]"?  "R6300v2"?  Other?

   Aside from the model-number confusion, that sounds like a very
incomplete description of what, exactly, is connected to what, exactly.
A cable has two ends.  (Hint: If a device has different types of
Ethernet ports, then "connected to device" is not enough detail.)

> [...] How can I get to the R3400 to configure it?

   One way would be to disconnect the "R3400" (whatever that is) from
everything except its power adapter and one computer.  Once you start
connecting multiple router-like devices together, things get more
complicated.  "More complicated" is different from "impossible", but
without some basic information about how this stuff is connected and
configured, specific advice (better than guesswork) is tough to provide.

> [...] but then it says it can't find the Netgear server.

   What, exactly, said what, exactly, when you did what, exactly?

   None of that is a useful problem description.  It does not say what
you did.  It does not say what happened when you did it.  As usual,
showing actual actions (commands) with their actual results (error
messages, LED indicators, ...) can be more helpful than vague
descriptions or interpretations.

   Are you using some web browser or other, with some URL or other, on
some computer or other, connected somehow to something (or not?)?

   Assuming that you're trying to add the WNDR3400[vX] to your existing
R6300v2 network to extend its wireless network coverage, you might want
to configure the WNDR3400[vX] as a wireless access point.  Sadly, the
details of that task might vary, depending on which which
hardware/firmware versions you have.  If it's a "v2" or "v3", then visit
http://netgear.com/support , put in your model number, and look for
Documentation.  Get the User Manual.  Look for "AP Mode".  For a "v1",
it should be possible, too, but perhaps more complicated.