sensiblue

Hi, This is my first post, but i have been reading and learning a lot from this forum. I have a problem with 5 ip cameras, first of all i bought dahua 1.3 mp , and dahua 16 ch NVR. Here is the problem, I set up this nvr in the front office and connected 4 ip cameras directly, No problems. At the back server room , where all main internet box (c-beyon and cisco router connected to it) i connected POE (48 V , 8 Ports) switch to cisco and connected all the remaining 5 cams to poe. First time it took some time to plugged each and configured their ip's. It worked about 2 days and all of a sudden , remaining 5 cams are blank , i scan the network, i don't see the cam's ips. When i restarted it still didn't see ip's on the network but entering manually on i.e., opens the login page , however, it will not log in it keeps saying wrong username / pass. First i reset , everything worked after 2 hrs , i left the system working , but less than 2 days , same thing. At first i thought there is a problem with the POE switch , I bypassed some cameras and directly connected 12V power adapter at the end. It worked , same thing less than 2 days again the cameras are lost. I really don't understand what i am doing wrong. I set the ip according to router's range 192.168.1.1--254. so i set them up like 192.168.1.150--155, subnet masks are the same , 255.255.255.0 , Def Gateway: 192.168.1.254, By the way router is set with static ip from C-Beyond. I contacted where i got the cameras from and they told me router and the nvr has to be at the same router, no switch nothing. I appreciate any help , since the problem doesn't look like POE, i must be doing something wrong with network setup. Thanks. Josh.

Thank you for all your replies. First of all they have C-Beyond Internet / Phone System , from the back of this device router comes in (Linksys Home Router WRT 120N) i will try it with a separate router and different subnet to test to see if it will last more than 2 days. Interestingly , cameras keep the same ip , for example i changed to 192.168.1.150 and i try to log in trough ie it shows the login page , but when i put the credentials it says login failed wrong username/password. Also same time i run a ip scanner on the network , it doesn't show the ip . 4 of the cameras i connected to back of the NVR itself. They are working fine, I changed POE and tested , still the same result. Tomorrow i will try it with different network and test it , I will post the outcome.