NAT is present?

I´m pen-testing a subnet, and when i scan the open ports i get something 
similar to this:

*.*.*.1

PORT    STATE SERVICE
80/tcp  open  http
264/tcp open  bgmp
500/tcp open  isakmp


*.*.*.2
PORT STATE SERVICE

80/tcp  open  http
              https
*.*.*.3

PORT    STATE SERVICE
80/tcp  open  http
              https

All the host of the subnet seems to have http and https open but when i try to 
connect to it a lot of then don´t back a response.
I thing that the .1 (seems to be a router) have NAT and open http and https por 
all the hosts (up or down) .
Can someone help me?

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