Hi Behman,
You can access cameras from another location if you set up port forwarding on the router they are connected to. For example, lets say your vacation homes external address is 75.75.75.75 and you forward port 8888 for "camera a". From any other network you will be able to enter "75.75.75.75" in the camera IP address and port 8888 to access "camera a" in the camera setup.
This website has port forwarding directions for a large variety of routers:
http://portforward.com/english/routers/port_forwarding/routerindex.htm You can find your external ip address by going to
http://whatsmyip.org.
If your camera uses rtsp, you will need to use port 554 as the "internal" port and for http you will use port 80. If you are unsure which to use, you can just forward both and try them.
For more details please see our article
http://www.sighthound.com/support/setting-sighthound-video-monitor-remote-location-eg-second-home